You're smart to go to SCORE for assistance... great organization.
I can give you a rough example revenue projection. You can change the number of cars per period as you wish. This will be very conservative. Increase your estimates depending upon your tolerance for risk.
Plan on doing a minimum of two cars per week for three months. You can beg, borrow or steal two customers per week by telling everyone you know and meet about your new business, former coworkers, family, church members, gym buddies, high end dealerships (not for their on-site work, but for their referrals), performance shops, kid's friends' parents, car and bike clubs, etc.
If you can pull off two jobs per week, doing a good job, and making more contacts each week, word-of-mouth will increase your business to whatever level you can handle. You must keep marketing indefinitely.
The revenue, obviously, would be the gross receipts from the two weekly jobs. You must set prices (numerous threads on DC) for your various services. The SCORE volunteer can use the revenue number, combined with your expense and capital estimates, to complete your financial projection.
A couple of bits of advice, strictly personal opinion:
- Stay mobile for three months... no rent expense, no tenant renovation, no signage, less expensive insurance... no commitments. At the end of three months, if you feel that you can succeed, go for the fixed location if you'd like. You can avoid unnecessary start-up expense until you have a proven business model; however, in three short months you do not develop a strictly mobile clientele, that can be difficult to transition to a shop.
- Buy as little equipment and supplies as you can for three months. For example, you may receive advice to buy a good quality carpet extractor. Great idea... I'd love to have one. And, you may have access to an extra $750 for the machine. I'd advise waiting until you are somewhat established before making that kind of financial commitment. Worst case, Autogeek and others ship overnight when you need something for a specific job.
- I don't know what your detailing experience is, so don't be insulted by this if it doesn't apply. Detail as many cars as you possibly can to gain experience... family, friends, neighbors. You will start to set the word-of-mouth machine in motion, and you'll learn valuable lessons. However, cut off the charity program when it no longer serves your purpose. Remind your buddies that this is your business.
-This one will generate lots of debate: pick a product line and stick with it unless you have a reason to try something else. I'm a compound, polish, wax, pad, and buffer junkie like everyone else at DC. But that's one of the traits that differentiates hobbyists from professionals in my opinion.
- Do not hire any employees for at least a year. Just don't. I don't have time right now to get into it, but you really have to have your act together to start managing staff, and trusting your clients' cars and your reputation to someone else.
- Again, I don't know your personal situation, but don't expect to live on the business for a good while. Talk to SCORE more about this. Living with your parents, for example, is a lot different than supporting a wife, kids and mortgage.
Best of luck, buddy! Let us know how you're doing.