Ztech
Firstly you need to find out on what houses you are going to use the trolley system on, don't just take in the front view of the property, but look at the back because this is where your problems will occur, for instance the houses that I mainly cover are the back to back type with long alleys leading to the back gardens.
Now these are ok if the access is clean and tidy which it never is so you will need to navigate over rubbish - bricks -discarded furniture - dead rats sometime live ones as well and when you have over come all of this you will find that the back gate only opens half-way and you have to try to get the trolley though a 2' gap.
I have looked at all the trolleys that are for sale at the moment and none of them can cope with what I require them to do. So I have just had to re-design my original trolley to fit my needs.
The other thing you have to look at is water. What do you do if you have quite a few houses to clean in one road, do you keep going back to the vehicle to fill up or do you carry all your water needs with you. Remember that you will use around 25 litres or more to clean 1 house when you first start, with this falling down after about 3-4 cleans to around 13 litres. If you think that you can just drive down the road and clean via the back this is not always possible, it all depends on the parking situation.
And finally what will you do if one of the houses you have to clean has no access to the back, do you take the trolley though the house, do you run a extension hose though the house do you forget that house all together.
So what I trying to say is that one method of cleaning will not work all the time and you will need to be very adaptable
Happy Cleaning