The risk is based on how you will use the TT. Are you going to go on long distance and frequent trips? Or are you going to park it in a campground for long periods of time? Mechanical issues are going to reveal themselves with heavier use, especially for things like tires, brakes, frame, suspension, etc. Things like water leaks and broken appliances will happen regardless of type of use.
Unlike cars, I've never been successful convincing my wife to buy used RVs. We would walk through a few on the dealer's lot and realize how poorly so many people treat them. Fabrics are ripped and have burn holes, wood is chipped, appliances are stained, and they have that "smell" in them because they are not kept clean. Every time I've sold an RV, the buyer or dealer has commented on how it still looked brand new, which is what I pride myself in.
this may or may not be a factor to you, but a TT that is 8 years old may also not have a lot of the modern conveniences of a brand new one. When we bought our 2014 unit, we got an electric water heater and powered awning, which have been two of the biggest improvements over our previous 2006 TT. Lighting the old gas water heater was a huge hassle, and so was the manual awning.
My opinion is that if the detailed inspection shows the TT is in good overall shape, and you have some mechanical ability to repair things (or if new to RV'ing, have the ability to learn on the fly, like I did), then there shouldn't be too many risks to buy.
But with every purchase, new or used, make sure this is the TT you actually want and you aren't just attracted to it because you can save some money over a new unit. If you aren't happy with the TT in the long run, it doesn't matter how much you spent...
