You can charge what you like, if you get the work happy days, if you're desperate to earn a crust you'll work for whatever price you put forward that you know will get your hand snapped off.
When I first set up I had a chinese snide honda to get me going, one of them with the quick connect nozzles, I cleaned a friends drive in 4 long hours. Charged him £130 clean. I cleaned the same drive earlier this year in 30 minutes on my own with much better kit that we've built up over time. This time I charged him £60.
The faster you can operate the more you can fit in, the more you fit in the more leads to word of mouth can be gained.
Pretty much every domestic job we do there's always a keep up with the jones' types and they'll snap your hand off if they're aware with the speed you can complete work.