I've been at it for about ten years, and usually finish right around 100K per year. As a fleet washer for the first seven years I used myself plus one helper, sometimes two and was able to keep labor cost at aobut 20 % including wages, taxes, and worker's comp. This was usually running one machine, sometimes two when I had two workers.
Over the last two years, I have switched from fleets to residential and commercial and have been able to do about 100K doing 90 percent of the work without help. It is pysically demanding, especially in the south Louisisna heat, but I much prefer keeping more of the income for myself without the headaches employees cause. I have rarely been able to hire a reliable, efficient employee.
The challenge for me is that 100k is about the max I can do alone in one year, and I do want to grow my business by having efficient, reliable employees. At this stage of my businesses I essentially have given up on trying to hire, and I am more inclined to keep working the way I am and waiting for the "right" hiring opportunity to present itself. I have wasted a lot of money, time, and effort over the ten years trying to hire good help.