I've had some touch and sews from that era. Those plastic gears will break eventually maybe right away or maybe later. For the T&S (if I remember correctly), the gears are about $60.00. The labor would be on top of that. You might check on the price of the gears.
So, no I wouldn't buy that machine unless I loved it and was willing to replace the gears. You can usually find a 401, a 501, a 403 or a 503 for $100. if you keep looking. They have metal gears and you can't kill them. There are also some nice Japanese models from that era that do not have the plastic gear problem.
bk