The ones that hike and fish all day are the best.

I use Zillow/Trulia for rents - very good tool, plenty of great leads .....but wouldn't sell a house without MLS.REALTOR.com is the most reliable source of info while Zillow is just fishing for your info and money from agents.These Zestimates are just jokes.

Are there any underground problems like old oil tanks from houses or other problems lurking?

The home used an underground oil tank (huge red flag for me).

It' not a buyers market if your only source of purchasing is by fishing in the same pond everyone else is fishing in, THE MLS.Off Market Deals will rectify that notion in any market and because you use HML and PML your CASH OFFER Negotiaions swings the market to sway in your favor.There are so many strategies for acquiring off market deals.

There are plenty of other fish in the sea for now. 

Use oil base kilz, that worked for me, stronger then latex kilz.

When oil was discovered nearby, oil patch workers flooded to the area, and our houses literally doubled in value. 

It sounds like they are trying to drum up business for candle/Tupperware/essential oil/Mary Kay parties, (the list is endless) or religious activities where all might not be welcome.   

The only (recent) cases in point I can think of, related to S/D imbalance, are the cities that experienced the fracking/oil boom phenomenon.