Joint Borrower, Sole Proprietor Mortgages: Who They’re For & When They Work

November 19th 2025

If you’re struggling with affordability on your own, you might have come across something called a Joint Borrower, Sole Proprietor (JBSP) mortgage. It’s a mouthful, but the idea is simple: someone else can help you borrow more, without owning any share of the property.

In this guide, we’ll break down how JBSP mortgages work, who they’re best for, and when they can be a smart solution.

What Is a Joint Borrower, Sole Proprietor Mortgage?

A JBSP mortgage allows an extra person (usually a parent or close family member) to go on the mortgage but not on the property deeds.

This means:

They share responsibility for paying the mortgage.
They don’t own any part of the home.
They’re not caught by the extra 3% stamp duty surcharge that applies to second-home ownership.

It’s basically a way to boost affordability without adding someone as a legal owner.

Why Would Someone Use a JBSP Mortgage?

To Increase Borrowing Capacity

If your income doesn’t stretch far enough on its own, a second applicant’s income can help you borrow more. This is especially common for:

First-time buyers facing high house prices
Single applicants
People with lower or inconsistent income

To Get on the Ladder Earlier

Instead of waiting to increase income, build savings or pay off debts, a JBSP mortgage can speed up the process.

To Avoid Family Members Owning Part of the Home

Parents often want to help, but don’t want to be tied to the property legally. JBSP works perfectly here.

To Avoid Stamp Duty Surcharge

If a parent went on the deeds, they may pay the additional 3% stamp duty. JBSP avoids this because the helper isn’t a legal owner.

Who Are JBSP Mortgages Ideal For?

JBSP is most commonly used by:

First-time buyers

Especially young professionals whose incomes haven’t caught up with house prices in their area.

Parents helping adult children

This is by far the biggest category. Parents can use their income to support the mortgage while the child owns the home.

Couples where one partner has lower income or credit issues

If one person can’t go on the mortgage (credit, affordability, past financial issues), they can still live in the property while the other partner and a helper apply.

Single parents

Where one income alone isn’t enough to meet lender affordability models.

Older borrowers

Sometimes adult children go on the mortgage to help parents downsize or move, though lenders vary on age limits.

How a JBSP Mortgage Works (Step-by-Step)

Borrower + helper(s) apply for the mortgage together.
Lender assesses all incomes, commitments and credit files.
Only the main buyer (the sole proprietor) goes on the property deeds.
The mortgage offer names all applicants, who share the legal responsibility for the loan.
Everyone must pass affordability, credit, age criteria and take independent legal advice.
Over time, the helper can often be removed from the mortgage when affordability improves.

Pros of a JBSP Mortgage

Boosts affordability significantly

Can help you borrow more than you could alone.

No extra stamp duty for the helper

Parents, siblings or partners help without owning part of the home

Flexible exit — they can come off later

Good for long-term affordability growth

Perfect for careers with strong income progression.

Cons to Consider

All borrowers are legally responsible for the full mortgage

If payments are missed, everyone’s credit file is affected.

Age limits can restrict mortgage terms

If the helper is older, their age may reduce the maximum mortgage term.

The helper’s borrowing may be affected

Their income is tied to this mortgage, which can limit their future applications.

Some lenders require legal advice

Independent legal advice is often mandatory for the non-owner borrower.

When Does a JBSP Mortgage Work Best?

When the main buyer’s income is rising

For example, early-career roles with strong salary progression.

When the helper has stable, strong income

Often a parent or relative with good credit and minimal debts.

When other options don’t fit

Such as when:

A guarantor mortgage isn’t available
A gifted deposit still isn’t enough
A partner can’t go on the mortgage

When avoiding stamp duty surcharge matters

A JBSP mortgage can work really well when one partner already owns a property and the couple want to buy a home together, but don’t want the existing property to trigger the additional 3% stamp duty surcharge.
Instead of adding the partner who already owns a property to the deeds, they can simply go on the mortgage to support affordability — avoiding the second-home tax charge.

**When JBSP Might Not Be Suitable**

If the helper wants to own part of the home → Joint mortgage may be better.
If the helper is near retirement → affordability may be restricted.
If the buyer’s income won’t realistically improve → removal later may be hard.
If multiple applicants already have commitments → affordability may still fall short.

Can the Helper Be Removed Later?

Yes — this is one of the best parts of JBSP mortgages.

Once the main borrower’s income improves, or once debts are reduced, you can request a remortgage or product transfer to remove the helper.

Is a JBSP Mortgage Right for You?

Every situation is different. A JBSP mortgage can be incredibly helpful for buyers who need extra support to get onto the property ladder, but it isn’t right for everyone.

Speaking with a broker gives you personalised guidance, checks lender criteria, and helps you choose the right solution for your circumstances.

Need Advice?

If you’d like to explore whether a JBSP mortgage could work for you, we’re happy to help.

Get in touch and we can run through your options, affordability and the lenders offering JBSP products right now.

What is Help to Buy Equity Loan?

Help to Buy is a government-backed scheme which helps first time buyers onto the property ladder. It was introduced by the government in 2013 and has been a huge success in helpingpeople buy their first home ever since. The scheme provides eligible buyers with an equity loan (also known as shared equity) of up to 20% (40% in London) of the value of a new build home, so the buyer only needs to raise a 5% deposit, with a 75% mortgage making up the rest. Essentially, with Help to Buy allows buyers to purchase a property with just a 5% deposit, making it a more affordable option for many.

The loan is interest free for the first five years increasing to 1.75% after. After this, the interest rate will increase each year based on the Retail Price Index. It is also important to note that the interest you are charged does not go towards paying down the equity loan.

What are your options to pay off your Help to Buy loan?

There are a few different ways that you can repay your equity loan. It doesn’t need to be repaid until you sell the property or come to the end of your mortgage term. However, you can pay back the loan earlier. This can be at any point after the completion of the purchase, and you can either pay the loan in full or make a partial repayment with a minimum repayment of 10% of the property value. So, what are your options?

1) Pay the interest – After 5 years, you begin to pay interest on your equity loan, this will be a fee of 1.75% of the total value of the loan. This will also increase year on year in line with the rate of inflation. It’s important to know that you will only be paying interest and your loan will not be reducing. If you opt for this, you must remember that if the value of your home increases, then your equity loan will also increase, resulting in you paying more when it is paid off. Not sure how much interest you’ll be paying? You can easily find a Help to Buy interest calculator online, we have linked one below from Taylor Chartered Surveyors:

Help to Buy Interest Calculator | Taylor Chartered Surveyors (taylorsurveyors.co.uk)

2) Sell up and Move – Many people signing up for the scheme seemed to think they would live in the property for 5 years, then sell up when the interest kicked in. In some cases, this is an excellent idea, especially here in the south where property values have increased (although as discussed above, bear in mind that this would also mean the equity loan amount has increased). The problem comes in places where property has decreased in value and you may end up with low or negative equity. In some cases, the homeowners would not have enough money to form a decent deposit to move on, and so would have to stay and pay the interest, or sell at a loss.

3) Pay off the Loan – If you have savings then you may choose to use these to pay off your loan. You will need to pay for a surveyor to value the property as the equity loan is based on current property value. The unfortunate thing about this is that you cannot pay off the loan in increments – you can either pay half of it, or the whole of it. The valuation is another cost that needs to be accounted for.

4) Remortgage – Remortgaging will allow you to pay off your equity loan and be left with one

mortgage to cover all of your borrowing. If your property purchase rises in the future, then

you will have saved money by paying your loan of earlier. If this is your plan, the best thing you can do in the first 5 interest-free years is to overpay as much of the mortgage as you can. This will give you a better rate when it comes to remortgaging. Bear in mind there will be fees associated with remortgaging and possibly with overpaying.

Take home points to remember:

• The equity loan interest payments will only increase year on year, cutting into your ability to save to pay off the loan. Taking a long-term view and accounting for these costs rather than burying your head in the sand is the best course of action.

• Lower cost areas where property values have not increased can leave the buyer with negative equity or not enough of a deposit to sell up and move out.

• You can only pay off the equity loan either in halves, or the total amount (in Scotland, you can pay off in quarters).

• Remortgaging options are currently slim.

How can we help?

Remortgaging is one of the most popular ways to pay back the equity loan. If you are considering repaying your equity loan in this way, we can advise you on a suitable mortgage and whether this is an affordable option for you. We are here to save you time and money by comparing deals across the market to find you the most suitable mortgage product.

It is worth noting that the outstanding loan amount will depend on your property’s market value. In order to determine this, you will need to instruct a RICS certified property surveyor to determine the value of your property. There will be a cost for this which you will need to cover.

If you would like to speak to an expert to get advice on this, we would be happy to help and typically do not charge you any fees for our service. Give us a call on 01844 390910 to book an appointment with one of our expert advisors.