I would say with 20% down your front-end/back-end ratios should be 28/36. In addition you need 6 months reserves at a minimum (i.e. 6 months of your monthly outflows), $5k or so emergency fund for unexpected maintainence, closing costs and you *may* need funds for furnishings and moving costs.

So, buying a home is not the *JOKE* many people have made it out to be in recent years, it is a HUGE commitment.