My OPINION:
IF you can dig into the coach and figure out the reason for the salvage title, give it a go. If you can get to the details, then you can look at how any problems were dealt with to get it back in working order.
If you are still comfortable with the coach after that due diligence, offer $50k and negotiate from there, to whatever point YOU feel comfortable with.
If you are planning (with some certainty) to keep it for a number of years, go for it. If you are one who trades frequently, selling it will almost surely be difficult.
If problems were dealt with properly, these can be outstanding deals for an informed buyer.