An increasing number of big lenders are devising low-fee banking products tailored to customers with troubled finances. The bare-bones bank accounts and prepaid debit cards are hardly big money makers; in some cases, they barely break even. But for the banks working to overhaul their public images, the products offer good will from regulators and a chance to woo customers who might become profitable in the long run — for example, if they start taking out auto loans, credit cards and other types of higher-margin credit. Bank of America, for instance, has introduced the SafeBalance account, which comes with a $4.95 monthly fee and allows for direct deposits and online bill pays while eliminating overdraft fees.