@Mark Baldwin I just bought a house flip with a bad foundation and my concrete contractor said you can either cut out the bad parts and replace them or replace the whole foundation.

There are five layers of possible involvement - (1) a 3rd party DD person, (2) the certified operator for the private util - that person should provide the sample reports, repairs, etc (3) state agency for all inspection reports - sometimes they can charge a fee if you request all historical to be pulled and (4) an engineer - based on age, you may find the engineering company that built it - if they no longer exist - then you may be able to find a local company that builds wells and can inspect certain things structurally. (5) Request code history from county/city for violations and any info they have on it.For septic, they are straight forward, you have to dig up at least 2-3, and verify the capacity/size reported and the material - seller may say they are newer but they may be older concrete tanks that are crumbling.

I am having a hard time getting any concrete information

If you sell later and its SF that was not permitted, you may have problems selling and with the county tax assessor and the city.Also, if you convert the garage, you can add a metal or wood carport in front of the garage for parking if that's important to you.Another suggestion, float in concrete so you don't step down into the garage.

Also, you need egress windows in the basement bedrooms, which often requires cutting into concrete and isn't cheap.

We ended up marketing the home with this insanely large concrete pad with its own driveway with nothing on it as a home with a "basketball court."

I am not aware of anything that would keep anyone from renting it no matter how low the ceilings or ingress egress etc.On my personal home i put a concrete vault  on the side of the house with stairs out side the window of the basement bedroom so open window step into the vault and climb up the stairs.. was not cheap .. but its safe. 

It's super important to buy in a newer concrete constructed building with a solid HOA. 

@Bryan Chuchta, I will try this again...perhaps a concrete example will help.Wholesaler Ben puts a property under contract for $100,000 and says "I will close in 30 days or less." 

Makes me feel ashamed to say "I have wholesaled  before".Me having several amazing video testimonials including from people I have wholesaled their property (knowingly) is concrete proof I am right!