If the side covers only need cleaning/painting, they could go for $50+ each, but if their nubs are broken off, that might be a stretch, as they would not just pop into place. (All prices listed, are retail, not wholesale... If you sell to a junkyard, you might get $50 for the whole shooting match, less, or nothing, if it has been picked over.)
Gas tanks, free of rust and dents, can sell for $200-$400, easy. At least, that is what I've seen them priced at on e-Bay, and Craigslist.com.
Instrument clusters can go for $100 and up.
Rims can go for $100 & up.
Frames can sell for $100 and up, but a clear title is important.
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If the chain is rusted, it will need replacing. The 630's are still available, or you can buy new sprockets, and switch it to a 530 chain.
The battery is going to need to be replaced -- count on it, unless it is a sealed unit.
If the seat will need recovering, a professional job will run you $300 and up, most likely. Call a shop, and ask what they estimate it will be. Custom piping, marine grade vinyl, custom foam sculpting, etc., will increase the price, but it was worth it, in my case:
link1,
link2.
Good luck with your budget. Remember, marriage is more important than any bike -- IMO. YMMV. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII