How to rent out my own house and buy another one?

[Kan Grrl]

We are owners of a home in Kansas City, MO. We've owned for about 7 years, but need to move to the Kansas side for school. Friends of ours have offered to lease our property so we don't have to sell in this depressed market. I'm very tempted but ideally want to buy another home right away, since rates are awesome and house prices are too. However, the bank we have our mortgage with doesn't want to give us 2 mortgages, even with our lease agreement in hand. There has to be a way around this...anyone know what the trick or approach is so that I can go ahead and buy another home now? Thanks ahead.