Well how big is the shop? Does it have a restroom/office/waiting area? Does it have a water/oil separator, a lot of places require that. Do you have enough capital? Can you take out a loan? How long to pay back loan, cover overhead, bring in work, and make a living?
Plans of marketing/advertising? How much $$$ a month will you plan on spending for marketing/advertising? Loaner cars? pickup/delivery/drop-off services? Do you have a website, business cards, company shirts?
How's the detailing market? Any other reputable mobile/shops around you? If so, how far? Is it the shop on a main street? Highly visible? Parking? Other automotive related shops around you, and how far?
Are you profitable on every job? Do you get caught on chasing every last swirl? Do you have your prices in order? Will you raise them?
Overhead expenses/start up: Clean up the shop- painting walls, fixing whatever needs to be fixed, plumbing, a washer/dryer if you dont want to take your towels home everyday, office/restroom/waiting area supplies/furniture. Monthly expenses: rent, water, electricity, insurance, alarm, internet, loan payments, equipment, supplies, staff
just a quick thought