If dirt--you'll need to install vapor barrier (heavy plastic) and gravel over that, then possibly some type of flooring.Is it a stone/rubble foundation? 

There isn't going to be any real ventilation in the bathroom, so you should wear a paint respirator with organic vapor cartridges as you put this on.Once you've got it spot primed, break out setting-type joint compound.

My 15 year loans cash flow, but it is vapors so any serious expense will be out of pocket.

The Complete reigns supreme as the stinkmaster world champion but the fumes are so bad that even if you wear a respirator with organic vapor cartridges it will attack your eyes.If you're paying contractor prices to get this done sight unseen in KY or NC, rip out all the hardwoods, roll the Kilz Max all over the subfloor (they'll refuse to use the Complete, and probably gripe about the Max), and do the luxury vinyl plank thing.

For that you can buy in a blue chip area, have security that it won’t vaporize, can manage locally, plus you have a good working knowledge of the areas dynamics since you already live here.

Where there's an air/vapor/thermal barrier, that's the thermal envelope.

first,  there are no kits that convert a gas water heater to the little vapors that the instant water heaters put out.  

They are not down lights and often are covering more distance than I need and 150w halogen or mercury vapor is an overkill.I also don't like battery operated LESs, I have a power source.I know they sell those socket extension with motion deyecyion for about $20, is this my solution?

If you are I would consider putting down a vapor barrier first, along with a sub floor like Dricore or some other dimple board to keep the flooring directly off the concrete.  

You can colleague me if you want to post that privately.The reason I ask is even if you land a loan at 75% ltv and the lender allows a seller second of 15% you will need 10% 200,000 to do this deal.Actually it will be more as title,survey,appraisal,phase 1 ,site inspection,vapor intrusion survey,and additional lender fees will be in the tens of thousands of dollars to close this out.