I guess it really depends on how bad your credit score is and what you call a decent rate. Your best bet is to really work on cleaning up your credit - get with a mortgage councelor and start right away with a plan. It may be easier than you think.
When you have bad credit, you are a huge risk to a lender (just look at what's happening in the market right now). If they decide to take the risk of giving you a loan, they will want to leverage that risk by charging you a high interest rate.
Several years ago, when 30 year fixed rates were in the low 5% range, I saw people with bad credit paying 12% interest or more. When you figure the payment, that's huge.
Bottom line is to focus on turning around your credit from this date forward and don't go back to your old ways. If you can't pay for it, don't buy it. Save your money for what you need to buy.
Hope that helps.