The good:
It is a somewhat interesting bike, in a vintage old-skool sort of way, and that's probably why you are interested in these.
The bad:
- Hard to find one at all nowadays, particularly one that has not been thrashed and stuck back together with chewing gum and duct tape. The few really good ones out there, either the owners are hanging onto them, or if they are selling, it is at a premium price.
- It is at least 22 years old -> Parts availability, or the lack thereof.
- It is at least 22 years old -> Stuff is going to go wrong. Are YOU going to know how to fix it?
- It is at least 22 years old -> Many mechanics won't want to touch them due to lack of parts availability AND due to lack of familiarity with two-strokes. Are YOU going to know how to fix it?
- It is at least 22 years old -> Bikes back then used rim and tire sizes that are now pretty much considered obsolete. You can get tires for them, but they're not comparable to modern tires that are only available in modern sizes for 17" rims.
- It is a two-stroke -> Knowledge in the industry about two-strokes is fading fast. Are YOU going to know how to fix it?
- It is a two-stroke -> Smelly, high fuel consumption, sketchy driveability (non noob friendly), smoky, come with the territory.
- It is a two-stroke -> Fouled spark plugs come with the territory. Are You going to know how to fix it?
The RZ back in the day was reasonably reliable for what it was, as long as people who didn't know what they were doing left them stock (which often wasn't what happened). But two-strokes are pretty much inherently not going to last as long as a comparable four-stroke.
In my roadracing class, the RZ350 is legal. But there are few of them still running. Every time someone shows up with one, it's pretty much assured that at least one weekend per season, that bike is either going to not want to start (and it's kick-start only, by the way), or run crappy for reasons that no one at the track can figure out, or foul a spark plug, or melt a piston and go boom, or seize and "squeak".
I know several people that have these bikes. None of them ride them any more on any sort of regular basis. But they won't sell them, either.
Way back when, it was time for me to replace my thrashed EX500 track bike, and it was between an RZ, or an FZR400. I rode an RZ in the paddock. It had the same crude, unrefined, coarse feel that the EX had and which I wanted to get away from. Bought the FZR400 instead. Still have it and still ride it
My suggestion ... consistent with everyone else's. For your first bike, buy something newer, that you can get parts for, and which is more likely to be stone-axe reliable. Ninja 250 or 500, CBR 125 or 250, Suzuki GS500 are all great choices. Maybe not as "unique" ... but for your first bike, you want something that you can get parts for and that everyone knows how to work on.