You're kind of talking abut two separate animals...backyard and commercial kitchen are very different. You wouldn't want to pay a five digit figure for a backyard smoker, but you might have to do that for a large commercial cooker that is allowed in an indoor setting. Especially if you are in the more populous south east Michigan, where codes are fairly strict.
In my neck of the woods, none of the current BWS models would be acceptable for an indoor setting. They require stainless interiors, smoke evacuation fans, sanitation certification and more.
I personally would recommend that you get yourself a good smoker and learn to use it well. A Fatboy is my personal choice, but others like the Party. If you want to cook higher volume and use it for a mobile kitchen, the Pro JR. is a very nice option. Once you understand the operation, you can look toward what you will need for a commercial operation.
To answer your questions:
1. Gas or wood/charcoal will depend on your local codes. There are cities that are now requiring gas for the main heat source.
2. This also depends on your city/county/state codes. They may require all of the venting, NSF certification, UL registration and in some places even require you to have a 20,000 + pollution control device installed in your chimney. (required in NYC and other cities for wood burning pits)
Have fun. I've done the restaurant thing...challenging and can be fun, but it's a lot of killer work!
"The Powers of BBQ"