Greatamericantrains.com has kits. It would be tons of fun!!
Loose the s on trains . . . www.greatamericantrain.com
22 grand for a "starter kit" is a little out of my price range or I'd order one today!
But you know . . . 3/4" iron pipe cut in half with plates welded on the bottom to fasten to the cross ties would make a pretty cheap (relitive to buying real stuff) rail. If you had a track and could find something to use for wheels, how hard could it be to fabricate a train to run on it? Hummmm . . .