American Home Mortgage is taking a baby step into the banking space by agreeing to buy a small bank, Flower Bank of Chicago, for $16.25 million in cash. The REIT wants the bank to “gain a franchise through which banking products can be offered to American Home’s customers as well as to the general public,” it said in announcing the sale. The firm is struggling with an earlier deal, though. Efforts to buy Waterfield Financial Corp., the mortgage business of Waterfield Mortgage Investment, have hit some bumpy legal waters.