First thing to consider is how hard is the water in your area - if it's soft then a di vessel is all that's needed - lucky so'n'so's - this could be left at home
If you have the skills then you can easily clean windows to the very best standard wether your one man outfit or have staff with the most basic items - in fact I would always suggest people start this way as you learn what the problems are and then address them by getting not only better equipment but the right equipment for you
My philosophy has always been only buy what you NEED not what you would LIKE to have
There are some that need big fancy vans and equipment to feel justified /superior - mentioning it at every opportunity like a badge of honor
It's great to buy stuff even better if you then do an in depth honest review for others and if if makes life easier so much the better - but if your cr@p at cleaning windows then no amount of gizmo's will alter that
I made my comments based on things like "old van" and "no kit" personally, if I had had time to look in the back I would have made the effort to say hi, and chat, find out why he works the way he does - you will learn one of 2 things - a different of working or the guy is an ar$€ 0le and you stay well clear
Darran