What Is an income booster mortgage?

This type of mortgage—professionally known as a Joint Borrower Sole Proprietor (JBSP) mortgage—allows family members or supporters to add their income to your application, which can increase the amount you’re able to borrow.

In simple terms:

• You’re the main borrower: You live in the property and your name is on the deeds.

• Supporters join the loan: Up to three supporters can join the mortgage to add "weight" to the application, but they aren't listed as owners of the property.

• More income, more power: Lenders may consider up to four incomes in total to calculate how much you can borrow.

Who can help?

Supporters are usually parents or close family members who want to help you onto the property ladder. They don’t normally need to live in the property, but because they’re part of the mortgage, they’ll share "joint and several liability"for the loan.

This means that while they don't own a share of the home, they are legally responsible for ensuring the full mortgage payment is made every month. Because of this commitment, most lenders in 2026 will require supporters to seek Independent Legal Advice to ensure they understand how this might affect their own credit and future borrowing.

How can it help?

An income booster mortgage can help you:

• Borrow more: Leverage multiple incomes to meet today’s property prices.

• Reach homes that might otherwise be out of budget: Open up options in better locations or with more space.

• Buy sooner: Move in now instead of waiting years for your independent salary to grow.

• Plan for the future: These are often used as a "stepping stone." The goal is usually to remortgage into your sole name once your own income has increased enough to take over the loan.

Ready for Lift-Off?

If affordability is the only thing holding you back, an income booster mortgage could give your plans the extra power they need. At Moat Mortgages, we help first-time buyers explore all the options available and find the mortgage that helps them take off onto the property ladder.