My parents are willing to lend me enough money so I can put down a 20% deposit on a house. I will pay them back interest free over the next few years. Do I need to tell the lender where the money has come from?
Yes you do. When assessing your ability to service the mortgage, the lender will want to factor in the loan repayments to your parents plus any terms and conditions set by them, and whether they intend to take a charge on the property. Alternatively, you could ask your parents to “gift” you the deposit instead. In this case the lender will require your parents to confirm in writing that the deposit is indeed a gift and will not seek repayment from you.
Obviously this will require you to have very generous parents!!