Here are my thoughts:
-Sign up for and take a motorcycle safety course. You will learn how to ride and get some idea if you enjoy it.
-A TW is a great bike to learn on and perfect for your needs.
-Sounds like a reasonable price if the bike is in good condition. You can always offer less and see if he'll take it.
-If it turns out you don't like it, you should be able to sell your TW pretty easily.
I'd say go for it. Not much downside.