Is foundation issues a deal breaker for buy/hold investment under 100K?
If it is minor and I plan to hold it for a long time, I may do it. If I plan to rehab and resell, it is usually a deal breaker unless there is a lot of margin in the deal. Even if you repair the foundation, you will have to disclose it to the end buyer, which can scare them away or reduce the value. There are enough deals out there without foundation problems for me to dismiss the ones that are going to be twice the work.
The technology has really come a long way. I deal with a local company that floats concrete under the foundation to fill the gaps and support the house. It expands as it hardens to create a solid foundation across the entire slab.