Peter,
The out-of-production DCS TIUs and Legacy Bases have used prices that are outrageous. Until new product is shipped later this year (we hope), the only relatively inexpensive way to experiment with command control gear on a layout is to buy an original (mid 90's) Lionel Cab1 base and remote. Mine still work fine. The basic wiring is a single connection from the base to the track and an alligator clip jumper works for me on temporary layouts. The TMCC signal and commands from the Cab1 will control the basic features of a Legacy locomotive plus switches, routes, accessories and trains. You can find inexpensive TMCC locomotives on the used market and the current LionChief 2.0 locos still use the original TMCC command set.
... or ignore the problem of acquiring unobtanium gear altogether and get on with running your trains:
Most of the latest Lionel locos offer Bluetooth control. No base needed. The currently available Lionchief app doesn't control all Legacy features, but the good news is it doesn't add any cost and gear to run your locos remotely.
