I love my Nak
(19 years and counting)
But I am dreading the day that it dies, or needs serious repairs.
As much as I like my Nak, I would not buy a used one, especially an older unit (even though they are soooooo good), for fear of repair problems.
By the way, I would hesitate to buy any used cassette deck (any brand) for the usual problems with moving parts, damaged heads etc.