This is a great source for used Otari MX5050 Reel to Reels on Reverb. This gentleman has years and years of experience working on, and restoring them, exclusively.
               
https://reverb.com/shop/genes-gear-outlet-40

He provides a detailed list of what he does to them to bring them back to spec. Most importantly, the heads are either like new, are relapped, or replaced with new. In other words, the finished product is as good as new. A bit on the expensive side, but by the time you were to buy one that needs work, and get the work done to it, you would end up spending close to the same amount. Why not get it right the first time?

He accepts offers, so you can talk him down a bit. I just purchased one from him myself, as I needed one with 15 ips capability.
He usually posts one at a time, so, cosmetically, you may have to wait for one that looks good, if that matters to you. The important thing is that each one he sells will perform like new.