You can do it! Be patient, ask lots of questions of the forum, weed through the negative responses, include pictures where it makes sense, etc. You may find a unit that has been well maintained and is being sold at a great-for-you price. You never know! If a deal sounds too good to be true, it probably is - that's when you need to take a step back and rely on the forum.
Some things I have learned from my many used camper purchases ($s are based on taking the campers to shops for repairs):
-Do not buy a unit that doesn't have a current inspection unless you can spend at least $3,000 and still be getting a good deal
-Do not buy a unit for which the current owner cannot demonstrate that all of the the RV systems work unless you can spend at least $1,500 and still be getting a good deal
-Test drive it - if you don't feel safe, you probably aren't