I would suggest a tire hammer to start. If you aren't interested in buildong one then there is a shop in Seattle that will build you one and put it on a pallet and ship it. I've considered an Anyang and I know friends who have one that are happy. But at $6k including shipping for a 33# vs $3500 for a 50# tire hammer w/brake I'm leaning to the tire hammer.
Anything bigger and you will need/want a dedicated foundation set in concrete.
Additionally, if you are forge welding perhaps consider a forging press. Same company in Seattle is doing a run of C-Frame forging presses that will be very versatile. With a press you don't have to worry about a foundation either.
There are several forge press manufacturers. Most are an H frame, but I prefer a C frame if well built.
Have you done any further research?