Adding a Family Member to Your Mortgage: What It Means (and the First-Time Buyer Trap)

Adding a family member to your mortgage is a popular way to borrow more — usually a parent adding their income to boost what you can afford. It can work brilliantly, but there are strings attached that most people don't hear about until it's too late.

The two main ways to do it

• Standard joint mortgage: you're both on the mortgage and both on the deeds. You both own the property and you're both liable for the payments.
• Joint Borrower Sole Proprietor (JBSP): a family member goes on the mortgage to support affordability, but only you are on the deeds and own the home. Not all lenders offer this — it's a specialist area where broker access really matters.

The first-time buyer trap

This is the bit that catches people out. If you buy jointly with someone who has owned a property before — which most parents have — you can lose your first-time buyer status. That can mean:

• No first-time buyer stamp duty relief — on a £350,000 home that's a £5,000 difference
• No access to first-time buyer schemes or LISA bonuses on a joint purchase with a non-first-timer
• If the other person keeps their own home, the purchase may attract the 5% second-home stamp duty surcharge on top

This is why JBSP mortgages exist: because the family member isn't on the deeds, you keep your first-time buyer status and there's usually no second-home surcharge. But lender choice is narrower, so getting the right one matters.

Other things to think about

• Everyone on the mortgage is jointly liable — if you can't pay, the lender can chase your family member
• The family member's age can limit the mortgage term (lenders have maximum ages at the end of the term)
• Their own borrowing is affected — being on your mortgage counts against them if they want credit
• Plan the exit: when will they come off the mortgage, and will you be able to afford it alone by then?