Here in Ohio you can check the County Clerk of Courts website and look up the homeowner, see if there is a foreclosure in process. You can also check the County Auditor's website to see who the current owner is, which would tell you if the bank has already taken it back. Not sure about other states.
As far as maintaining the property, the bank may have an issue with it, but generally I wouldn't think they would really care as it is less hassle for them. As far as the home being vacant, if it is similar to yours (design, square footage, bed/bath counts, etc.) then it would be better if it is vacant rather than selling at a steep discount. The value of your home is dependent upon comparable homes that have sold. If your market has a high percentage of foreclosures, then that is the market. On the other hand, if foreclosures don't make up a good portion of the market then it is possible an appraiser would not use that sale as a comparable.
Zillow, the "zestimate" that it gives is pretty useless. I would pay more attention to the RECENTLY SOLD properties that it shows. Compare square footage, bed/bath counts, lot size. Comparable home sales are what determine the properties value. Another resource is http://realestatecenter.bankofamerica.c ... value.aspx
which will give you a range (sometimes a pretty wide range) for the property value. It will also give you a list of the homes it used as "comparables", although sometimes it is way off.