Weight of a usable wheel?

[marty in Ohio]

I picked up a 19 inch wheel and tire this weekend. The tire was shot but the wheel is really straight. It's rusty, but I think it can be blasted and painted for use. I heard that there is a certain weight after the blasting that can or can't be used. Anybody tell me what that weight is? And what can I expect to pay a sand blaster to remove the rust?
Marty