We’re in upstate NY where the pipes in crawlspaces may freeze.(2) I will move the water heater (which, ironically is for the upstairs unit) from the mud room to the basement area beneath the upstairs unit (but accessed through this unit).

I agree with you that if there is clean up and it leads to an area beneath the structure of the property, tthan the clean up could be much more than the amount of equity in the deal.

I even offered a few Newbies here in El Paso to bird dog for me but they think it's beneath them.

This was a rough property, and clearly beneath me.A couple weeks later my client told me how he had a new commercial property he wanted to buy, but needed $10,000 to make the deal go.  

Many would dump the water right next to the house where it would accumulate into large puddles during bad weather and eventually leak into basements OR even worse saturate the soil beneath your homes footer causing it to sink slightly and causing cracks in your foundation which may let in more water.  

No job is beneath me if it means I get to learn the ins and out!

This makes the land beneath a house worth more than the house itself. 

LLC with which all other properties LLCs fall beneath it seems most appealing to us.

My thought is that the only way this house would be available ever, is if the first bank foreclosed..that would wipe out everything beneath it.But in this situation - what happens?

That means it's not load bearing with out a wall beneath it.