to get parts for resale, I'd think you'd have to be the one breaking down the machines.
As for selling them at shows, I'd concentrate on common vintage, you'd need a 60 ft van to
carry your stock for all the machines mentioned here.
It isn't something I'd look for at a show, I'd be looking on-line.
For shows, rather than follow the herd with Featherweights I'd concentrate on collecting
Singer 301 404, 99, and sell the actual machines themselves.
Or specialize in needles, both common and uncommon. Higher mark-up, lighter to pack and carry
Keep us posted!