If you are going to get an Analog scope... watch for a Tektronix 465, 465A, 475, or 475A. They are all basically the same except for bandwidth:
465: 100MHz
465B: 100MHz (with improved performance (in what ways I don't know))
475: 200MHz
475A: 250MHz
These scopes have XY mode as well, which is good for testing the vector output of vector games.
Any of the above should pop up for $50 - $150 depending on included probes, DM44 DVM option, etc.
Always try to get a scope from someone who has used it. Hopefully they'll be honest, and they can at least give you history, any glitches/etc.
The units I mention above can require cleaning of the many contacts that the rotary selectors control. I have 2 myself, and one does require cleaning, as it can be a little glitching when selecting the volts/div on channel 1.
There are also many great resources on fixing these scopes should you find a problem, as they were produced for many years with many units sold.