A stored bike is not a lost cause. However, the "negative" posters are correct that you need to be aware of the costs of inheriting a used bike. This applies to any used bike though, and I'll bet a lot of posters would agree that a used Ninja 500 is a great first bike, and would suggest against buying new when it's your first bike. That said, this is perhaps one of the cleanest, lowest mileage Ninja 500s you're going to find, right? So it's a reasonable purchase as long as you approach the pricing (and your friend) appropriately.
One suggestion I've not heard is to let a dealer handle everything. This bike will need brake fluid and most novice mechanics are not comfortable handling corrosive brake fluid and learning about brake bleeding, not when brakes are so critical. You could come to some sort of nice agreement with your friend and the dealer to look it over and estimate the refresh.
If you buy new from a dealer you'll pay for the set-up, too.
Another factor to consider in pricing is tax. In California, people often forget when comparing prices to include the substantial tax and registration fees, which you will have to pay even for a used bike at the time you register it for your new title.
Some have suggested changing your own tires. This is in fact easy to do but not if you've never done it! (I used to work in a shop and have changed hundreds, maybe thousands, of tires.) And while you can spoon them on easily enough if you know how, balancing the tires requires a balance stand and weight kit, which is going to run you a bit of change. Even now I take my wheels into the shop to mount up new rubber so I can use the electonic balancer. I'm such a grifter, I tell ya.
Finally, you can't always agonize over every $50 in your quest to be on the "best" side of a deal. Come to a reasonable agreement and then accept that you have a new baby that will cost you money for all kinds of things down the road.
