Foreclosure auctions give a whole new meaning to buying "as is" because you often can't gain access to inspect the interior. You may see what you're getting on the outside, but short of peeking in the windows into dark rooms, you have no way of seeing the inside conditions. Even if the homeowner is still living in the house, he isn't likely to welcome you in.
The problem with buying a mystery box is that if the homeowner failed to make payments, then the home could be in disrepair. If the home has been sitting empty, the damage could be significant.
You can try calling the bank to see if the representatives will grant you access. They may agree since they are highly motivated to sell the property. If you can't get a peek inside, however, you'll need to factor probable repair expenses into the total amount you're willing to bid on the house.