old duplex, A+ location, foundation issue - what would you do?

[Yulia J.]

Here is the picture: a 100 y.o. duplex plus a basement unit. Great desirable location. The basement unit could be rented out but it would be illegal, so we consider this property just a duplex with a basement as a bonus. We were told that the duplex was moved from a different location about 30-40 years ago. Some issues have been addressed recently - roof, windows, etc. With increased rents, it would cash flow.  Bedrooms in 1 of the units are small, and the layout is awkward. But the main concern is a foundation issue. The owner said they have recently put 80K into fixing the foundation. The property was contingent 3 times in the last 6 months, and all the deals fell through. Last time it was on the market for 7 days, we offered on it and lost to the other offer. 2 weeks later, the deal is dead, and the seller's agent is contacting us. The fact that the last 3 deals fell through and the fact that there has been something wrong with the foundation makes me feel suspicious. You could probably read between the lines that I don't have much experience yet. What would you do?