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.

Interest-only mortgages are very appealing, as they enable people to afford a property by only paying off the interest over the term of the loan.

At the end of this, the equity needs to be paid off, which normally happens when the homeowner sells the property.

However, if they want to remain in the house, this might cause a few problems.

What is an interest-only mortgage?

Interest-only mortgages are typically offered to buy-to-let investors, as it reduces their monthly outgoings, meaning they can keep more of their rental income.

When they sell the property, they then pay the financial provider back the price they originally bought it for with the proceeds.

For instance, if they bought a house for £120,000, this is how much they would give back to the mortgage company when they sell it, even if it has doubled in value and is now worth £250,000. This also allows them to earn a tidy profit of £130,000 from its increase in value.

Repayment mortgages are different and are typically given to owner-occupiers. These involve paying not only the interest on the mortgage, but also some of the value of the property.

Therefore, by the end of the term, whether it is 20, 25 or 30 years, the homeowner would have paid the £120,000 plus all the interest they owed to the bank. If they then sell it for £250,000, they can keep this cash for themselves.

The issue for interest-only mortgages comes when owners reach the end of their term but do not want to sell their asset.

Managing your interest-only mortgage

There are various ways you can go about managing your interest-only mortgage over the term of its lifetime. For example, you could consider overpaying when you’re able to as this will reduce the amount you owe, as well as the interest you’ll pay on the loan.

Common ways to pay back these types of mortgage include selling your home, switching to a capital repayment mortgage, making overpayments, using savings, pension lump sums and equity release.

What to do if you cannot afford your house at the end of the loan?

Unfortunately, the difficult economic situation, with soaring energy and food prices and mortgage rates, has meant that many people have been unable to save as much as they hoped over the last couple of years.

Therefore, if you live in a property with an interest-only mortgage and the loan is coming to the end of the term, you might be facing the conundrum of needing to pay off the house but not having the spare cash to afford it.

BTL landlords who do not reside in the home have the option of selling it, and using this money to pay back the mortgage provider.

Although house prices have been declining lately, and have dropped by 3.2 per cent over the last year alone, they are still likely to be higher than when they bought the property if they purchased it years before.

Indeed, the average house price is still £40,000 above pre-pandemic levels, so there is a good chance the sale of the property will cover what they owe on repayments.

If, however, the value of the house has fallen since it was bought, the owner will still need to dig into their savings or take out another loan to fully reimburse the mortgage provider.

Those who aren’t BTL landlords with an interest-only mortgage and want to continue living in the property need to find an alternative way to raise the funds.

1. Call the lender

It is a good idea to contact the mortgage provider as soon as you can, so they are made fully aware of your financial position.

They might be willing to extend the term of the loan, helping you to stay in the property for longer.

Unfortunately, this is likely to mean the monthly payments will go towards paying more interest on the asset instead of reducing what you owe on the home.

2. Take out a repayment mortgage

Alternatively, you could contact a mortgage broker to find out whether you have a good chance of being given a repayment mortgage for the remainder that you owe.

This might be harder the older you are, as the term of the mortgage will be shorter, but it is worth seeing what is available if it lets you remain in your house.

If you think you want to stay in the property indefinitely, you might want to consider a retirement interest-only mortgage. This enables you to pay off the interest until you either move into a care home or die, after which the property is sold and the sale reimburses the financial provider.

This option means homeowners do not have to worry about having to move out. However, it means they will forever be paying off interest on the loan, and will not be able to leave as much inheritance to their loved ones as they might have hoped.

3. Move out

Although many people do not like the idea of moving out of their home, this could be their only realistic option if they do not want to keep paying for a mortgage.

By choosing a cheaper property or downsizing, the sale of their house could pay off their loan, as well as mean they can live in their new home mortgage-free, which could provide them with a huge sense of financial relief.