Make sure that you close with a local title company who will offer you title insurance not just a title search, almost every time I've purchased something from auction.com there have been title issues that the bank didn't want to pay to clear but I've insisted, and they've relented.
You either have to get inside the property before bidding, or you need to bid assuming you'll need to do a full gut rehab, or you need to gamble a bit. But even if it's been vacant for years and there is some mold, that doesn't automatically mean full gut rehab... you might need to replace some drywall if there was water damage but the electrical, plumbing, HVAC, etc. should still be mostly good especially if it was winterized.
Buy J. Scott's book on this site about estimating rehab costs, there's no way to just ballpark a budget without knowing scope of work... you could be looking at $10/sq ft for mostly cosmetic work with builder-grade finishes and low-end appliances (i.e. $15K budget) or $100/sq ft for full gut rehab with luxury finishes (i.e. $150K budget). Your costs will also vary depending on if you are looking to live here yourself, or rent it out, or flip it.
Good news is that it's fairly difficult to be "screwed for life" from just a single real estate purchase. ;-)