The greatest feeling in the world is picking up a bike for a couple hundred bucks that "seems" like it should run (no sign of rust, engine turns over, carbs don't look terrible etc) only to fill it up with gas when you get home to find that it breathes.
You can get CB450s for cheap. Not from eBay or restored ones (they fetch a good amount), but you can certainly find them.
CB450K5: Paid $600. Didn't "run", but seemed otherwise healthy. Got it home to find that it didn't run because the fuel tank was empty. Compression was "fair", but still pulled good. Eventually did a ground up resto because it would slip out of first gear, and it leaked some oil. Check out my "Sunrise" thread.
CB450K7: Paid $400. Replaced the forks, handlebars, and a couple various other parts, and now have something that could be shown at a show. Check out my "Brownie" thread.
So don't think what you have is what you have to stick with. Post a wanted ad for a CB450 and that's how you will find the amazing deals. If it's posted on Craigslist, it's fair game at a fair price. The wanted ads is what gets the stupid-deals. Oops, let out my secrets.