The problems you list don't sound like major issues.
Handlebars and Fork Seals are fairly easy to replace.
https://www.z1enterprises.com/fork-seals-35x48x11.htmlI wonder why they wern't done when the rest of the bike was being assembled?
It started on the first kick, but had it already been started and warmed up before you got there? Does it have a title? Any oil leaks from the engine? There are good and bad things to be said about the mileage. Airbox or Pods? Have they fiddled with the jetting with that exhaust? Dent on the tank or is that supposed to be there?
If you like the bike buy it but as stated it's gonna take some elbow grease. No better way to learn then to dive it headfirst.
Would I buy it? Probably not-I'm more of a stock type of guy with these, although I do like the look of it. The current set up is an expression of the prior owner. It's also often harder to resell something customized compared to stock. Also, I'm kinda cheap- non running CB550 around here would be more like 800-1200 probably for that. A fairly perfect CB550 in my area would be around $2500 but again, you're going to have to know the prices in your area. Bikes are fairly plentiful i.e. don't rush into a deal if you're not 100% sure, Another will come along.