Inspector said slab is sagging. Is this a deal breaker?

[Bruce Clark]

I have a deal under contract for three small houses that are right next to each other on the same street.  The total price for all three is $64k, so I understand and expect these houses to have some issues. The Inspector looked at all three houses. For two of the houses, he did not find any significant issues - need some gfi outlets, a window does not close properly, roof is old but is not leaking etc. 

However, with one of the houses, he said the slab is sagging. He said the living room and kitchen on one side of the house are significantly lower than the bedrooms on the other side. He said he cannot tell when this happened or how much of an issue it is. He said it may have just settled that way and not be an issue, but he cannot tell.

I have no experience with houses built on slabs. All of my houses are on underground foundations. What should I do? Is this a big deal or not much of a concern? Is there a way to fix this for a reasonable price? Should I attempt to renegotiate the price for all three or tell the seller I just want two of the three?

Any and all advice is welcome. Thanks in advance.