Would you consider a Class C that was used to tow?

If you can do it, checking the condition of the ATF, then pulling the transmission pan and looking at the debris in the bottom along with a road test should tell you what you need to know.

Generally, burned fluid, excessive metal shavings with lots of soft clutch material combined with less than positive shifts or slipping in any/all gears should be of concern and a major deduct in the sale price should you decide to proceed. ATF leaks of any kind are a concern but not necessarily a deal breaker.

Chum lee