You forgot somewhere to store the water at home.
Also barrels to transport the water in whilst in the van, unless you're only using one knapsack of water a day!
Does the 99 squid for the backpack include a charger?
R.O pipework for the DI unit.
Fittings etc for knapsack.
I don't store water at home and you don't need a water tank either, a friend of mine fill up his backpack at the customers house with his di unit.
There is a charger with the backpack.
You don't even need a van, at christmas I used a corsa with no problem at all, I even was able to fit my carpet cleaning machine in as well as the wfp equipment.
This is a very basic system that will get anyone up and running with wfp, as you earn, you can then upgrade to a more indepth system.
If you want to make excuses for someone not to go wfp then there are many, but these people will not be very sucessful in business, a sucessful business person looks at how to overcome problems rather than let the problem overcome them.