The mobile deal is the way to go, there is a guy I used on and off for last 20 years, he is a preacher but has a sand blasting system.
He does have a policy that if he comes to your place, its a minimum of $850 to make it worth while, I think that is fair.
A lot of times, when I'm ready he is booked up for two weeks and I end up blasting myself, that is the only drawback to him is he is busy.
Another friend who owns a restoration shop in the GA mountains, just opened a sandblasting and soda blasting shop next to his body shop.
It was a $45,000 investment and when asked I said you are nuts, well he smart enough not to take my advice and the guy has been booked solid since second week and has hired two extra guys. He is getting about $1000 for 69 camaro type car in and out.
Great business, for sure.