My personnal views on this incident. Have bought quite a nos of items in buy&sell forum. Before you venture into 2nd hand goods, you must be prepare that it is always a risk involve in relabaility. It may not fail in few days time but down the road you cannot tell. If you can't accept this condition and buy due to the attractive price, you are decieving yourselves.
In 2nd hand market you can't expect seller to give any sort of warranty except on the sopt testing. Some nice seller may give a short warranty time like 3 days for you to test it out at your place.
If the seller wants to be through with his sales he can do the following
1) Dismantle the item that is for sale for visual inspection
2) Assemble back and test it out if possible (if not possible to test probably let the buyer test it out himself in the next 3 days)
3) Get the seller to sign an acceptance form for the transactions. (This really helps as mutually they have agreed to this sales by testing and visual inspections)
Most seller maynot go to this extent as it is a hassle. But the acceptance form is good as later there's nothing much to argue with.