+1 on the compression gauge. My dad made me buy him a 1979 CB750 locally. Looked really good, and was 100% complete. Even the tires were new.
Only problem? Cylinder 1 was trashed, which I thought was simply a fuel issue. a Compression gauge would have told this story. Either way, he was happy to rebuild the motor....got the bike cheap enough. Seems to be his favorite year, though I don't like it because of the sloped seat which is made for smaller riders.
My recommendation for your first bike is to get something that is solid, even if it's missing some exterior stuff. That's what I did. I bought my CB750 off eBay. It was missing emblems, covers, crappy battery, tires were cracked, fork ears were cut, needed new chain/sprockets, etc. But the engine was 100% solid which is what matters: I didn't have to touch that or the carbs. No leaks. Ran like a champ. I was able to basically drive it, while replacing those types of things.
I still haven't touched the carbs. The fuel is flowing very good.
THe longest my bike has been on the motorcycle stand was two months, and that was in during the winter season. Gave me a chance to finish everything up.
Point being, don't get something that you have to tear apart as your first bike.
ALSO, unless the owner provides clear service history or documentation, plan on replacing tires, tubes, brake pad/shoes, chain, and sprockets.