People expect me to say price. Sometimes it is. But if I had to point to one thing that unravels a deal more than any other, it is financing.
A buyer gets pre-approved, makes an offer, and everyone celebrates. Then something shifts. A job changes. A big purchase gets made before closing. The lender takes a second look and the numbers no longer line up. Suddenly the deal that felt solid is on shaky ground.
The frustrating part is that most of these situations are avoidable. A pre-approval is a snapshot, not a guarantee. Anything that changes your financial picture between the offer and the closing can affect it.
So my advice is simple. Once you are under contract, keep your finances still. Don't open new credit, don't finance a car, don't switch jobs if you can help it, and talk to your lender before you make any big money move.
Inspections and appraisals cause their share of collapsed deals too. But those usually come down to negotiation, and negotiation can be worked through. Financing that quietly falls apart at the end is harder to recover from.
The best protection is communication. When everyone stays in touch and problems get raised early, most deals hold together. It's the surprises that break them.