A little story, because it's not just about making a fair rate—it's about how much your customer is willing to pay.
I once worked for someone who made widgets—literally hundreds of thousands of the same little part. He was a specialist, and few others made that part or could make that part like he did. He had about a dozen customers who bought as many of those widgets as he could make. To one client, he sold those widgets for $5 a piece and sold them by the thousands. For another customer, he sold fewer widgets, but he charged $50 a piece, and the customer was happy to buy them from him. He was profitable on both, but he knew where he could increase his margins. When he was asked why his prices were so different, he said, "because you have to know the pain threshold of your customer to know what you can charge them for any given service. This customer has a low pain threshold, this one has a high pain threshold."
I asked him how he knew what each customer's financial paint tolerance was and he responded, "ahh, see, that's the magic."
I think the price someone is willing to pay for a specific service is going to be different from person to person, neighborhood to neighborhood and state to state. Your experience, location, quality of work and a lot of other factors will go into the rate you can demand. Look around your area for an idea of what local detailing shops are charging (not quick car wash-type production lines), and put yourself in the same ballpark. And don't be afraid to adjust your prices slightly as you go—not discounts to everyone, but adjusting for your market overall as you go.
I'm in the same boat trying to establish my business locally, make enough so that it's worthwhile and profitable and get enough work to keep my schedule full. It's WAY harder than making a car look good.
Good luck,
doug