1. Yes under 20. I started when I was 17, partially spending the time in my Compsi vocational class doing client work I had found on odesk(now upwork).
2. First couple jobs I probably worked below minimum wage. Lots of foreign competition on odesk that is hard to compete with no reputation. By the end I was making 35/hr in an area where you can mortgage a house for $350/mo (why did I move to the bay area again?? :))
3. Yes they get easier to get. Part of my pitch was I get things done right which people liked.
Edit - another fun fact about odesk. My first office job in the bay area was literally across the sidewalk from them. I spent three years getting work through there, moved 3000 miles, and ended up across the street from their office. Neat right?
Was 2nd client easier to get. How about the 50th?