A "not high end" TT on craigslist should be priced $30 or less, so spending $30 to test it doesn't pass the "makes sense" test unless you've been wanting to buy a phono stage anyway. I've bought six turntables on craigslist, only two of which I heard play music before I bought. Three of them I never even saw the table turn, one of which I knew to be broken when I bought it (paid $5). I take the seller is saying that it worked last he used it. If you think he's honest then plug it in and make sure the platter spins and any automatic functions work. (Bring an LP you don't care about with you.) If you're still concerned then if you can get access to an ohmeter it's pretty easy to check continuity of the tonearm wires (what you really care about -- the sound produced will be more a check of the cartridge than the TT.) If the price is more than $30 then maybe you should pass. (you didn't say what turntable this is. I interpreted "not high end" to mean "low end mass market")
My opinions are free and worth twice that.