I found that there is a seller out of Toronto that auctions aroung the second day of every month. His cabs go for 300-500 CAN$.
I had decided to build a custom cab with new controls. I spent 250 on buttons and joys, and 120 on keyboard and optical encoders. I still will have to spend about 100 on plywood and then some for t-moulding and paint.
As you can see, it would have been cheaper to spend, say, 275 on a cab, and then clean it up and replace any buttons or joys etc that need it, paint it, and be done.
Personally I wouldn't count on fixing up and selling for a profit. Chances are that you'll invest more in repairs/restoration, than you can make back.
I'd say, restore if that's your thing and you want an all orignal cab. Mame an existing cab if you want the cheapest mame option. Build custom if nothing less than your perfec, ideal machine will do.