You might try testing your idea as well. Start with one car. How much demand for your car is there in your area? You can advertise in a newspaper, on Craigslist, or on eBay Local. That way you minimize the amount of money you put in order to find out if you have a profitable idea. This post about testing small business ideas might come in handy as well.
I like the "Muscle Fit" part. But marketing seems vague. There are a lot of other types of marketing services out there. Is it ok from an industry standpoint to include the words copy or copywriting in the name of your business?