If you want ease of finding parts, buy a Honda.. just being honest. Im not sure about the SR bikes, they arent too popular in my area. With the XS bikes, you are either paying a bunch, or buying used. Most of the internal engine parts are unavailable new and you will have to research on compatibility.
Performing a compression check will tell you what you need to know. If the seller says “oh it just needs new rings” i would walk, probably run. I would walk if the engine needs anything internal.
Externals arent a big deal, carbs, side covers, things like that. Lapping valves isnt too big of a deal either but you still have to crack the engine open.
Whats wrong with the SR?