I suppose someone could measure the interior walls instead of exterior, but it shouldn't make that much difference...

Was given an estimate of $500/year but sounds like a waste of $$.

My only concern is that because it has 2 meters and the house flows more like multi family than single family I might just be wasting a-lot of money.

The only time Im that high are for serious unknown problems like a caving foundation wall, or if we are talking properties in the $1 million range.

I've been thinking of contacting other wholesalers in my area for their wasted leads: Low/no equity, meh motivation.

They will most likely try and recruit you to come to them...so, that's why I would stay away from the big places, someone will let you do it...you just have to be careful not to waste your time on old or stagnant listings. 

The the sellers can properly make an educated decision, but then how many people would want to buy a house where the foundation is end of life and to fix it is a 20k expense.The void wall is not that big of a deal as long as the home can properly cool or heat, which I believe just roof insulation and the right tonnage will accomplish. 

A complete waste of money and natural resources....

I'm trying to learn approximates for my market before I start wasting peoples time. 

Reinforce changes to the property aren't allowed and state it in your lease (no painting, wall building, wall moving, etc), talk about specific lease restrictions (e.g. no pools and trampolines, limits to guests, animals) on lease signing.