I have a fold up ping pong table in my basement I bought for $50 on CL. Might get you started.
Welding aluminum would be a no go. I wouldn’t have access to a welder (and I don’t have any skills for it). Isn’t it really hard to weld things actually flat because they bend in the heat? Especially aluminum?
If the table is really simple, I would make mine out of wood anyway. But I like working with wood, and I already have all the tools.
Doors in the US are about that size too.