Depends on the condition. If it has not been restored I would say $400 based on ebay pricing but start lower. Thorens need TLC to get up to snuff. If the table has not been properly maintained then that means more work for you. And don't just take their word and let them just turn it on and let it spin. Look to see if there's fresh oil in the bearing well. Ask if the belt is new and original. Have them play a record. If they can't do that, get firm on your price. If they've *never* played anything on it through amp and speakers, haggle it down. Let them know you'll have to pay a lot to get it in top shape. These are complex machines.
You'd be surprised how many people try and sell tables by just turning them on and saying 'see, it works'. The less the seller knows about the table, the less you should be paying. These are old *and* complex machines. I highly recommend reading up on the 125 and knowing it's in and outs before meeting the seller, including searching things like 'Thorens 125 repair' so you get an idea of some of the common issues people run into. As a newbie the last thing you need is to throw good money after bad if the table turns out to have serious problems.
And I would *HIGHLY* recommend you ask this question at the Turntable forum at Audiokarma. AC is great, but the table forum at AK is probably the best vintage turntable forum out there. If you posted there you'd have a bunch of answers by now.
And yes it will stomp your Project into the ground.
