Joint Borrower Sole Proprietor is one of the most underused ways for families to help first-time buyers. It combines the affordability boost of a joint mortgage with the stamp duty benefits of a sole purchase. Yet many brokers never mention it.\n\nHow It Works — In a standard joint mortgage, all borrowers go on both the mortgage and the property title. With JBSP, the parent (or other helper) goes on the mortgage but not on the title deed. The buyer is the sole legal owner of the property. The helper's income is used for affordability, boosting borrowing power by tens of thousands of pounds. But because the helper does not own the property, their existing home does not trigger the additional property stamp duty surcharge (currently 5% on the entire purchase price). This saves thousands.\n\nThe Stamp Duty Saving — Consider a 300,000 property. If a parent who already owns a home goes on the title as a joint buyer, the total stamp duty would be 17,500 (standard 2,500 plus the 5% surcharge of 15,000). With JBSP, the buyer pays only 2,500 as a first-time buyer with standard rates. That is a 15,000 saving on day one, just from the structure of the ownership.\n\nAffordability Impact — A first-time buyer earning 35,000 might borrow approximately 157,500 at 4.5 times income. Add a parent earning 55,000 to the application and combined borrowing rises to approximately 405,000 at 4.5 times combined income. That is an extra 247,500 of borrowing capacity. The parent does not need to contribute to the deposit or the monthly payments — their income simply supports the affordability assessment. In practice, most lenders will use combined income but may apply different multiples.\n\nThe Key Trade-Off: Term Length — The mortgage term is usually capped at the oldest borrower reaching age 70 or 75, depending on the lender. If the parent is 58, the maximum term might be 12 to 17 years. A shorter term means higher monthly payments. A 200,000 mortgage over 25 years at 4.5% costs approximately 1,111 per month. The same mortgage over 15 years costs approximately 1,530 per month. Buyers need to ensure the shorter term is affordable on their own income, because the parent may want to be removed from the mortgage in future.\n\nWhich Lenders Offer JBSP — The scheme is not available everywhere, but a growing number of lenders support it. Barclays was one of the pioneers and offers it across most products. Halifax allows up to four borrowers with one proprietor. Nationwide offers its Family Mortgage product with similar mechanics. Metro Bank, Bath Building Society, Mansfield Building Society, and several other regional building societies also participate. Each has different rules on maximum number of borrowers, acceptable relationships, and how they assess the helper's existing commitments.\n\nRemoving the Helper Later — Most families plan for the child to eventually take over the mortgage solo. This typically happens at remortgage. Once the buyer's income has grown (or the outstanding balance has reduced through payments and house price growth), they can remortgage into a sole mortgage. The helper is removed and their liability ends. This usually requires a fresh affordability assessment showing the buyer can manage alone.\n\nRisks for the Helper — The parent is jointly liable for the mortgage. If the buyer stops paying, the lender will pursue the parent. The mortgage appears on the parent's credit report and affects their own borrowing capacity. If the parent wants to remortgage their own home, the JBSP commitment will be factored in. These are real risks that families should discuss openly. A formal agreement between the parties is advisable, even though it is not legally required.\n\nJBSP vs Other Family Support Options — Guarantor mortgages (where the parent's property is used as security) carry different risks. Family offset mortgages (where the parent's savings offset the child's mortgage balance) require the parent to lock up cash. The Bank of Mum and Dad (gifted deposits) requires the parent to part with money permanently. JBSP does not require the parent to provide any money or put their home at risk — only their income and their credit commitment. For many families, this is the most practical and lowest-risk option.