Unknown Craw Space

[Kurt Key]

Hello BP!

I got an offer accepted for a single-fam that will be converted into a duplex here in Cincinnati and while going through the inspection we came across a big unknown. There was an addition to the home, which the home was originally built in 1891, and put on in 1997. There is no known access point to the crawl space and it is speculated that it is built upon a slab. However, there's a vent on the back side and there's no reason to have a vent if it was built on a slab, correct?

To add salt to the wound I tried contacting the previous owner who made the addition with no luck. I am trying to negotiate a credit for other issues, but is there anything else I could do to limit my liability on this if I can't get to look at the crawl space? Anything to negotiate for?

Thank you!