Given the depressed prices of many former top-line models, it hardly seems worthwhile to bother with the low end stuff.
But even former high end can cost a pretty penny when a CLA is involved... that is unless you have the resources to get it done cheaply. There's not many places that still do that type of work inexpensively. This is the reason why I would proceed with caution.
Fortunately for me, one of the good business relationships I have developed in the years past involves 4 older chinese gentlemen in an old hole-in-the-wall with more than 100 years accumulated experience in repairing old cameras. All my stuff, including very expensive Leica stuff that would require a trip to Solms, Germany have been repaired by them fairly inexpensively.
But I digress.....
Here's something no one has pointed out....
You can actually buy not-yet-classics cheaper than many of the "classic" mechanical cameras mentioned. Their younger age and updated designs (electronic shutters) make them ideal for consideration (age and lack of use alone will kill older cloth shutters). Furthermore, they are not considered classics, collectables, nor sought after for replacement parts... you don't have to compete with others on price.
Example... Canon EOS A2E, which was considered a wonderful camera of its time, goes for between under $40 bucks. Want to take advantage of FD lenses instead? The last FD body the T90 which is the top of the line professional body goes for about $50-100. Heck one of my all time favorites the Elan II (because of the dial layouts, eye-control and red focus assist) is a consumer body going for $10.
Many of the suggestions will come with nostalgic reasons.... unfortunately the popularity of these models also drives up price and the older the body the more likely it will require a CLA.
In summary... looking for a cheap user? Look towards the less popular younger cameras.