I recently was given a machine to pass on to a friend. When I took my embroidery machine in to the shop to get the needle threader repaired (cost me $10.00 and was done in a matter of minutes... no labor charge!), the repairman told me it would cost about $100.00 to tune the old machine. I bet the machine wouldn't get $75.00 at a garage sale. He told me it would make better sense to spend a few dollars more and just get a brand-new simple machine. He said he would do a $15.00 trade-in on the old machine because he could use it for parts.
I wouldn't be surprised at all if he required a deposit on repairs when the repairs are worth more than the machines. If he doesn't, then he should definitely make sure that he gets a signature that makes him the owner of the machine if not paid for within a certain amount of time.