For me, it takes about 5-7 hours for cars ($180) and 7-9 for vans and suvs ($220) inside, out and engine. That's wash, clay, sealant, wheels/tires, trim, windows, shampoo interior, clean/dress vinyl, clean/condition leather, degrease engine. I charge extra for more than light tar, tree sap, paint overspray, extra soiled interiors, etc. I charge $40/hr for buffing and wet sanding. I'm part time and have been charging money for about 5-6 years.
I get virtually all my business from Craigslist. Put up a nice clean ad, links to your website, and have quality before/after pics and you will get customers. Don't charge too little (if you do quality work) because you will scare people away. I have some of the highest posted prices on Craigslist in my area and I stay busy. My clients are frustrated with the lack of quality with high volume shops and come to me to have the owner doing the work.
All that said, I used to take a couple days on a full detail and charge like $80, but I had no insurance, no extractor, no steamer, only a DA, limited tools and limited knowledge of chemicals. It takes a lot of practice to do it right under 8 hours in a standard job and that's if you have the right tools. My extractor and steamer changed everything.
Keep in mind that I'm talking about daily drivers. I'm not talking about show car work that can be much more intensive. Evaluate the customer. I talk to them about their goals to match the right package to their vehicle. I'm not buffing out a car that will go through the cloth wash next week!