>>1147819It isn't cheap. 7 1/2" gauge seems to be the most common ridable "backyard gauge" in the U.S. Modelers usually model in either 1 1/2 inch to a foot for standard gauge or 2 1/2 inch to a foot for narrow gauge. you'll see everything from a guy with a loop in his backyard running a battery powered box cab to huge clubs that have literal miles of trackage. The biggest club in the U.S. has 23 miles of mainline rail and is still expanding. A basic battery powered box cab locomotive kit runs in the $4k range. A pair of EMD Blomberg trucks with tractiuon motors installed will run you $3K for a pair. Whe your building a steam engine, you can build entirely from scrach from plans, or you can buy unfinished major components like wheelsets, steam chest castings and steam fittings and the like, or you can buy a "turn key" engine for the price of a luxury car. There's 1 1/2 scale propane fired 2-8-4 Berkshire for sale on one of the sale sites for $53K, but that does include a two axle transport trailer and a scratch built reefer with the propane tanks in it. The engiones are real and generally run between 150psi to 200psi of boiler pressure, but I've not heard of anyone being seriously injured. Having a live steam engine hissing, roaring and chuffing between your knees will focus your attention. Here are some videos.
First up, a guy who has a loop around his residential property in Casper, Wyoming
https://www.youtube.com/watch?v=wTluwSdAT4o&t=10sNext is a large club in Sacramento, California
https://www.youtube.com/watch?v=S2k-TJLnwlQFiring a 1 1/2 inch scale 4-8-4 Northern
https://www.youtube.com/watch?v=DHtcHQXV_n4&t=11s 