Have a look on
www.window-tools.com it will explain all about pure water.
Also I've noticed that you are not earning a lot at the moment and you might feel that you can't afford a trolley system, if so, what you can do is buy just the basics to start with, and then build on that when the money starts to come in faster, which it will.
The basics you will need are
An RO or IO unit with Resin (send a water sample to peter at window tools he be able to tell which one you will need) An IO unit is cheaper but is only econmical if you live in a Softwater area.
The first 3 poles that peter supplies which go up to 18'.
The Cleaning Brush with Water Jets and angle neck
Pump Box
10 water containers
TDS meter
50' of 10mm water hose
1 Battery
Hope this helps