He also built all the deep cabinets underneath the 4inch Live Edge slab.

For some reason I did not take many pictures during the process and actually have no before shots with all the carpets, but here is what I do have.Two of the bedrooms had this glued linoleum underneath the carpet. 

But septic regulations vary by state (and areas within a state) and soil conditions can vary from lot to lot. 

From environmental standpoint, u may want to collect groundwater samples along boundary of the property with the gas statiob to see if it has impacted groundwater as well as soil gas samples to see if there is potential for vapor intrusion.if groundwater not used, then principal environmental risk would be vapor intrusion which can be effectively managed with radon system and vapor barrier.Note that if the gas station is downgradient from your property (gwvflows towards gas station), vapor intrusion can still be a problem since vapors can migrate thru sewers, utilities and any conduits.

Including first floor units; What I mean by that is that within the walkway, some first floor units also have chairs, benches, toys, hoses, shrubs that also equate to a “tripping hazard” To me it seem they’re singling me out: “you need to move it, people are tripping over it” I am completely respectful of other people’s comfort within the walkway and I went as far as to measure what area is underneath the patio perimeter of the twin unit above me, and I sawed off a partition of the legs.

If you go vertical and park underneath or can use on street parking you don’t need as much land at all.

I would get the soil in the basement excavated and put up a foundation wall.

If it's the latter, without too much information it sure sounds like your unit caused the water damage via overflow of the sink basin and/or a leaking S-trap underneath your sink when your drained the basin. 

.- Any soil contact with posts on wood-frame elements like a deck or patio?

Hi, I found an apartment that I love but in the bulding there is a oil tank with soil contamination.