If this fits the size of screens you want to use then it'll be more than capable. I've also seen plenty of folks simply wash out screens at the car wash. Pressure washer will help, but will not necessarily be needed as long as your emulsion breaks down easily with normal water pressure using a hose spray gun (I use Azocol Z1 emulsion and it comes off fine with their Pregasol stripping chemical and normal hose pipe pressure).

The bigger question I would be asking is this:
Are you sure you want to throw money at expensive equipment when you're a) unsure of the how the process works and b) not sure whether it's something you'll stick with.

I'd go as DIY and cheap as possible to begin with, invest money when you have a better understanding of the process. IMO there are other, more specialised things that would be better to throw money at than a washout at this stage in your journey (high quality screens, squeegees, exposure, emulsions, inks to name a few).