Twin lens reflex (TLR) camera has been available for more than a century but it was until the Rolleiflex was released in the end of 1920 that the camera becomes a hit until the 1960’s when the rangefinder camera took over the market.
For the cheapest yet antique version of the TLR, one can get a Lubitel camera for roughly $70. Lubitel made TLR are from Russia and dates back to as old as the 1950s. Lomo has also released a newer version of the Lubitel called the Lubitel 166+ but that would cost at least $300.
Those that are up for it could definitely get a hold of a Rolleiflex or a Rolleicord which are a bit more expensive. A working Rolleiflex would be at least $200 with the best ones costing thousands but nevertheless, expect the best quality possible with these models of TLRs.
If you are really in a budget but would like to give this camera a try, you could spend around $30 for a Recesky DIY TLR Camera but it would take time for you to assemble it properly. Nevertheless, it is a definitely as close as you can get on a budget for a TLR camera. Whatever camera it may be, having these would be nice as it will be a new experience of taking photos.