Hey GS allow me to chime in really quick.. A couple months ago I started RC Gunworks LLC.. That is my firearm restoration / refinishing business. After several years of doing the same thing you've been doing as a hobby and doing work for co-workers and friends I decided to go pro and open my own shop. I've got my Type 01 FFL (which is required to be a licensed gunsmith) and all the equipment I need "right now"... It took me a long time to get what I've got and I see the need to buy more every time a new or repeat client comes in. My shop is also run from my home (shop in back of property) which required that I get permission from my city gov. I can perform pretty much any firearm finish a client would like including hot caustic bluing but I prefer the slow rust blue which is more durable in my opinion.
C3 already posted that you should have business cards to pass along. To that you may want to consider going on-line with a web site.. Check mine out at: www.rcgunworksllc.com
Nothing fancy but it will help get you business. Also.. reach out to the social media stuff like twitter and facebook.. Amazing the kinda press you can get from that. Canvas the local gun shops.. tell them what you can do and bring pictures or a sample of your work to show you are a serious craftsman and not just a shade tree gunsmith.. Everybody tinkers.. This is a business you are gonna want to make money at.. You must decide too is this is to be a business or just a hobby cause when word gets around, you will get busy. And the first time you drop the ball and piss off a client, you're done..
I wish you all the luck in the world. I've not made a profit yet, but I am getting more clients each week.. LOL I dropped off a few cards at the shop where I get my haircut and so far I've gotten two new clients and 4 new guns to work on. Most everyone who's posted is right about the kind of work you will see most: Cleaning and parts replacements. If you've not already done so, make sure you have accounts set up with folks like Numrich and Brownells.. There are also several vendors that specialize in hard to get or obsolete parts for older firearms.. Research the internet and acquire schematics, books and anything else you can get on every gun you can think of. Remember also, the internet is your friend! Use it like you did here for advice and information...