I did it back in the early 2000's up to around 2012 but it got difficult with customers wanting something for nothing. I guess they figure if they're a friend of a friend of a friend and because my shop isn't a "real shop" they can try to take advantage....at any rate the simplest of ways to say it:
-LLC. DON'T DO A SOLE PROPRIETORSHIP. NO NO NO
-Good heavy duty concrete and put in an asymmetrical hoist that will pick up a heavy pickup truck, like a F-450/F-550 size rig. Many small biz owners have larger than average light trucks that would love being able to bring it to you instead of a dealer, and if you can pick it up, bonus.
-Good lighting, no shadows. LED spoils me now. wish I had it years ago. I put lights at ground level it was amazing for undercar work.
-spend the money on oil and hazmat containment. Flammable cabinets are cheap used and having a real place to drain used oil will help you in more ways than one, especially if you live in a socialist state like CA or WA. Tanks are expensive but not prohibitively so and many companies will come get it for free. OR, if you need heat, you can burn it in a waste oil furnace.
-get a commercial reseller account with every parts store you can. Especially ones who will deliver to you. NAPA, O'Reillys, etc. Also look into getting an account with a wholesale distributor. Around here in WA places like Competition Specialties, Seattle Automotive, etc will deliver to you direct and they also supply the parts houses, dealer parts depts, and your competitor private homegamer shops.
-PAY YOUR TAXES. Don't mess around, these days too many people use plastic cash for everything, so when you take CC or debit they'll find you eventually. Which brings me to..
-GET SET UP TO TAKE credit cards or debit cards. Yes there's a fee and yes they only reconcile a few times/month but the convenience for your customers will help you in the long run.
-Get the correct insurance, bonding, and make sure any and all local licenses and permits are up to date and valid.
-Be realistic. Don't be afraid to say NO to a job. Too many people are afraid to turn down work but the horror stories of biting off more than you can chew, or chewing on the wrong thing, will haunt you forever. It runs some guys right out of the biz all together.
-Buy a good scan tool and keep it updated. There are more ways from Sunday to debate how to select one but narrow down what you WANT to work on (don't say everything, be realistic) and go with it. Later on, you can always ADD something else.
-if you choose to, or are already certified/licensed, doing AC work is a money maker because the machine does most of it for you. Instant second guy when you can bring on AC work, or expand your abilities being able to do a job that requires AC system R&I. Like a VW Passat heater core lol, no seriously, say NO to that one.
-Network with local shops. We're all in this together, if you do a leveling kit or small lift kit or a steering rack, or tie rods, or some struts, blah blah blah, have a guy down the street who will align it for you. Work WITH your fellow wrenches and you'll get work sent YOUR way just as much as you sublet or turn people on to someone else. Like me, I won't do VW work at home even though I own them because I don't like working on them, but I'll send it all to my buddy's independent Euro shop in return for him sending me his customers who have diesel truck issues. Win win.
-I used Mitchell OnDemand, I think it's called ProDemand now. We have it @ work too but my home subscrition was around $100/month and came with much more than just the flat rate time standards. It gave updated access to OEM bulletins, campaigns, quick fix it tips, etc and they had another higher level that would do all the back office invoicing and inventory controls too. For that I used basic Quicken software and some **** I found in the App Store for basic accounting. Never really needed inventory control or payroll as it was just me and I wasn't high enough volume to have a 'stock' of much stuff.
-If a customer wanted to use their own carried in parts I made it known up front there is ZERO WARRANTY if the part fails. They will pay time and materials for me to repair that failure. If I messed up, I'll eat it, but if the part messed up, they're on the hook. If I sell the part(s) my distributors will work with me and I won't charge them for warrany fixes. Anything you can sell them you can make money on, and normally you'll be able to sell them something for the same price they can purchase it for locally, but you're reseller commercial account will give you a few bucks of profit there. Even oil over the counter at NAPA, for example. You can make a few bucks off that for a simple oil change.
-Menu pricing works, too. Crunch the numbers and look at your prices. Many times you can flat price things like brake jobs, oil changes, etc. outlier vehicles you can fine print disclaim that there may be a difference in prices but for most categories of vehicle, you can make a profit by pricing brake jobs, timing belts, trans services, coolant flushes, etc all the same.
-I wouldn't do heavy engine or drivetrain work unless you're good at it and like it. 6.0 Powerstroke head jobs for example are a big money maker or a big money loser, in a hurry, depending on your skill set, tool selection, shop capability, and desire.