You want a deal. You have credit issues and not a lot of money down. OK, I understand that.
So: Why do you want a foreclosed home? Pardon my cynicism, but is it to remind you of your financial circumstances? That's the only reason I can see.
A foreclosed home is bank-owned. A bank's going to take a solid offer; it's already been burned once and has no intention of selling the home to someone who already has credit issues and little money down.
Are foreclosed homes good deals? Some are. A lot aren't. So you can't be looking because you're looking for a good deal. There are a lot of other good deals out there.
As for the advice to get prequalified first--that's fine if you can. But with credit issues and not a lot of money, purchasing conventionally (especially a foreclosure) isn't going to work for you.
So: Why are you looking for foreclosures?
Why not look for properties with owner financing. Or start by looking for mortgage programs that are designed for folks in your condition. Or work on cleaning up your credit a bit. If you're really interested in buying, start there...not by asking to look at foreclosures.