The council will not charge for a pitch as a rule as your license will cover you to work on public ground etc( i think) but i would not say your trailer will require 3 sinks, my old one never had 3 and it was not an issure. Best bet is to speak to your local council/ EHO as regs do change quite fast.

Are you thinking of doing this full or part time out of interest, and are you looking at investing a "reasonable" amount of cash or just a few k? Not being nosey, just its easier to give advice knowing more of the situation (sp?)