Go look at them, do some test rides, make sure anything you get FITS, and works ok and is in good shape. I don't get the sense that you're in this to fiddle with an antique. Due to age (10 for the Trek, 20-30 years for the roadies) it's anyone's guess how much wear they might have or how they've been maintained, you'd have to go look.
The Trek you posted is a fairly modern hybrid which is a lot like a mountain bike with bigger wheels, with trigger shifters, and it has lots of screw holes for racks, fenders etc. It would make a great commuter. Of the others you posted, the Prelude was an entry-level racing bike from the factory and lighter and nicer, with brand-name components and double-butted chromoly tubing in the frame. The others are basic transportation from before the mountain bike fad.
You can look up the Schwinns here
Schwinn Catalogs by Year
And the Raleighs here
Retro Raleighs
And the Trek here
2004 7500 FX - Bike Archive - Trek Bicycle
You shouldn't worry too much about finding parts for any of these. If something modern from a bike shop or mail order won't bolt up, you can find new-old-stock parts on eBay.
If you become serious about year-round commuting you may also want to budget for racks, bags, lights and fenders.