Any economics text book will tell you that what I have said is true. They have to keep some money back in case there is a run, the rest I assume is invested in stocks/shares. A lot of the money that keeps the economy going is simply printed - it is not backed by gold reserves like it used to be. WRT houses and mortgages they do of course have the "value" of the house to fall back on, assuming it has not been artificially inflated.