Why would it be crap?
Its exactly the same parts you'd find in a commercially available system,.. sourced cheap and assembled yourself.
The £550 would be for a 100GPD RO/DI 4 stage filter, a couple of water buts, Shureflo pump and pump box, battery and charger, a cheap pole, some 20 litre drums, and a DIY trolley.
Not exactly a top of the range setup,.. but a good starting point.
Once you're earning, you add the van tank, hose and reel, a backpack and a couple of better poles,.. but you re-use the pump, battery etc. You might even upgrade the RO unit,.. but its all stuff you can do once the cash is coming in. The £550 setup will get the ball rolling, and is perfect for domestic work.
There is a great DIY WFP forum that is well worth a look for some money saving tips.