Without an inspection by independent termite control expert you have no way of knowing if termites gone, even with owners re-treatment . Without a qualified building inspector you have no way of knowing extent of old damage. How much is too much? That's up to you, how much are you willing to pay to make repairs? With out inspections, you pays your money and takes your chances. If I could not afford inspections, I for sure could not afford repairs. I'd pass. Electrical box pulling away from house is not good sign, if owner doesn't care to fix what can be seen, how diligent has he been about what can't be seen?