Two years ago I found an old Schwinn Varsity 10 speed at a thrift shop (all steel, heavy and built like a tank). Haven't been on a bicycle (I'm a motorcyclist) since my teens and am 46 now. Anyway, I bought it to use as a commuter, put on new tubes/tires, cables/housings, chain and repacked all bearing except the rear sprocket cassette which I cleaned. Everything worked right but the bike turned out to be way too small for me and was very unstable. Tried to find a trainer stand so that at least I could get the benefit of some stationary riding, but could not find a unit that would accept that old bike's rear threaded axle and nuts. I saw one or two home made versions of a stand, but none seemed to be stable enough to safely use.

Money is a MAJOR factor in my bike commuting/hobby.

Questions:

-Are there any commercially produced trainer stands that would safely work on that old bike?
-Are there any safe homemade plans for such a trainer?
-I LOVE the old (1970's - 1980's) French road bikes like Peugeot, Motobecane, Gitane, etc... (never had one but always wanted one). If I get one of those bikes with a larger frame and refurbish it, are there any modern, affordable rear axle/sprocket cassettes available for that bike that will accept a modern trainer stand?
-A non-biking friend says that I should just go to Target or Walmart, spend a couple of hundred on a large frame, plastic hybrid bicycle thing and be done with it (frankly this just disgusts me, but I'll try to keep an open mind - remember, money is a real concern for me {don't have much}).

Anyway, all well-meaning feedback is appreciated.

Thanks!!