I also share my concerns regarding the gas station property as John Carter. As investors, it's all about the numbers and if the costs to clean up far outweighs the benefit, I'd just not pay my taxes so the county can take the property away for (not from) me.
However, if the county is aware that the property is contaminated or if it is on the Superfund list, the county must remove the property from the auction sale. But due diligence is still your responsibility.
I was watching a piece on Warren Buffett and he mentioned that he only invests in what he knows. Also a beginner in tax deed myself, I would steer clear of commercial properties as there are greater chances that those properties can be contaminated. Gas stations, auto repairs, dry cleaners, industrial chemicals, etc... There is a reason that these property owner did not pay their property taxes and allowed the property to be foreclosed upon by the county.
To answer your original question regarding the differences in the auction offerings of different property classes is that the only difference that I am aware of is that residential properties becomes eligible for auction sale after 5 years of delinquency, whereas it is 3 years for commercial. All other (disposition methodology, auction rules, redemption period, statutory challenge, and others) are the same.
[ Edited by lithiumcove on Date 12/17/2007 ]