If it is in the walls and we know what it may be (tobacco, pet, etc), we have a recipe (tsp, rinse, seal, paint)... or if it is from the floors, we clean or even pull the flooring (seal underneath refloor, etc)...One simple carpet one I use is sprinkling the large (13.5 lb)  bags of baking soda into the carpet (if carpeted)... work it into the floor with stiff broom, so it gets into carpet to pad.

@Daniel Moctezuma, I don't have any direct experience but the problem that I see is if the tank leaked you may have an environmental clean up on your hands (need to clean up the soil as well) - it may not be as "simple" as only removing the tank. 

I am unsure of the legality of this but I've heard it done successfully by others.Keep turning over rocks until you find something exciting underneath. 

Is you need to put money aside for foundation issues its not if Its when.. everyone of my homes I had we had some sort of work to do to address shifting soils..

There are a lot of people that have a bad house that they need out from underneath of.However, I have realized many of these people have waited too long to get help and I just can’t help them.

when I took up the allure the plywood underneath was damp in the hallway

Texas is very tough for a CA investor.. sky high property tax's  soil and foundation issues bad hail storms.. and your income taxed in CA.. so for me its a value add sell market.. make money but do not hold in texas.. but even that only the locals do very well at it.. its a tough place. you need the non income tax to balance the property tax's and other issues.

If there is a hazmat spill from an UST they bank won’t underwrite the loan w/o remediating the soil especially if near wetland.

I'm a new investor in the utah county area, I have been doing the calculations for numerous deals Provo,Orem,Springville,Payson,Eagle Mountain, Salt lake, American Fork, Lehi etc. and I have put in 8 offers in on properties in the last 2 weeks on multi families to single family homes and condos and all have been swept out from underneath me because I am only able to house hack these properties so I can only put down the 3.5% and I get the deal taken from me from other investors that are putting 20% down and paying over asking price for all properties.

Luck was with me, I met him at the Gym. a couple months Later, I did reserch for him for foreclosure properties, the best property I found him was a 3 unit with a bar underneath, He sold it a couple months later for a very good profit, He gave me 10 grand for the work.