Shaun
We use 2 honda 3000psi producing 15litres pm, which we find covers all our needs both domestic and commercial, we also have a lombardini diesel which is mounted onto a 1000L bowser. If you'r looking to do this professionally imo you can't go wrong with genuine honda (if anything goes wrong you can get them fixed), the important bit is the max psi and flow rate. If you go for a 3000psi you will need to use a tank, a wheelie bin makes an ideal tank. As for FSC we use both whirlaway and mosmatic (there are also other manufacturers but we have not tried them so can't comment) and really there is nothing to choose between them, I personally prefer the whirlaway 20" (I think 20") with wheels, it's ideal for most domestic jobs. Other bit of kit is an adjustable twin lance for edges and rinsing, and a snow shovel for collecting the debris you wash out (don't wash it down the drains).
We started by cleaning friends and family drives and patios to learn what and how, it's not rocket science but like everything it requires thought and practise.
Hope this helps.
Good luck.
Neil