It depends on the lender, but most lenders won’t need a deposit to give you a Right to Buy mortgage. They’ll usually be willing to use the discount you received on your home as a deposit. Because of this, the Right to Buy scheme is a good way to get on the property ladder if you have a low income or can't save up lots of money.
However, some lenders might ask you to put down some cash up front (around 5-10% of the property value) regardless of the Right to Buy discount. That’s why finding the right lender is so important when applying for a mortgage.