I will experiment with what’s underneath it first.  

Make sure you get a soil test first.

I asked him to push the reset button underneath and he said, "I rented an apartment specifically so I would not have to do maintenance."

All is done, but the floors.I pulled up the old carpet and it was in pretty bad shape, but there are wood floors underneath.  

Pretty low maintenance while maximizing the use of the space. https://blog.homedepot.com/backyard-makeover-pergola-with-bohemian-style/As for the front yard which is a sloped hill (pretty steep) overtaken by weeds, I'm thinking of planting native grasses to MD a section at a time to avoid soil erosion. 

Strip it for sure , it ill be more expensive but they can also check the wood underneath .

We get properties like this in neighborhoods with expansive soils, and EVERY house has stair stepping and issues above door frames, around windows, etc. 

im a new investor.i found this property that seems like a solid investment. the only problem is that the soil needs to be tested incase it contaminated by the oil tank. my problem is that if the soil is contaminated (no previous insurance) i would have to fix it because the seller (bank) is not willing  to do it.

@Bettie CampbellA few things:Is there a soil boring report to confirm soil bearing capacity?

Tank sweeps are usually done by a separate company, because if they find the soil has been contaminated, they know all the steps needed to re mediate - an inspector might be able to sweep for a tank, but I think each carries different types of Liability/Insurance.