I am guessing that you could have it rideable for about $500. That is better than spending a couple grand on a rideable bike that is going to need $500 worth of upkeep in 6 months. Any used bike with some age on it will nickel and dime you to death.
Totally true, compression and seeing if it starts would be the ONLY starting point. Otherwise, it might be just a dud!
You seem to be asking rather a lot. Compression and seeing if you can get it to start might be more reasonable. It'll likely take some fixing.
Sadly, I doubt you can realistically fix bent forks, and new one's are expensive. Might be a good idea to confirm used part availability and price before you do much to it.
Don't know about this specific bike, but a good start is to remove carb bowls and clean the carbs. See if it fires on ether; after you get it running, get forks from ebay and you're all set. I don't see you even putting 500 bucks into it if it's in halfway decent shape.
I was given a 1989 600 Ninja a few years ago that was wrecked. I installed the engine in a Yamaha Warrior sport 4 Wheeler that originally had a 350cc single cylinder. That thing was scary fast! 70 mph high gear wheelies required only a blip on the throttle. I sold it before I died having fun....
As many have mentioned, see if the engine will fire and the if transmission shifts OK. Before doing that, drop the oil and look for chunks and filings just to ensure you're not trying to fire a severely damaged engine.
Many, if not most Japanese bikes use common forks (Showa for instance). I'd venture to say that finding forks will not be an issue and will likely be fairly cheap.