Report Here's Why Banks Want 25% Deposit From 1st Time Buyers... in House prices and the economy Posted June 27, 2009 From the inside.... very simply, banks have being doing their risk assessment properly this time. They estimate house prices are going to drop around another 25%. So not to be left with debt, they are asking 25% to cover their themselves! So what about the 90 and 100% mortgages that have started to come back onto the market? You live in dreamland. This is the bottom.