You can get the 750kg payload (too small for two man) and the 1000kg version. (barely adequate)
I wouldn't - maybe hubby and wife team 3/4 day a week 7 hour day team but you really want a physically bigger van with a 650L plus a couple of 25L barrels and a two man team on all day work will need 800L to be safe.
I've still got my 56 doblo (736kg) and it was fine as a one man 400L. Now it has a 200L, and space for the guttervac and generator.
I have to agree with this comment of Gold's.
You have to buy the right van for a 2 man setup and in our experience you need something with a higher payload. So you would need to be considering Transit 280, Transit 300, Ducato/Relay/Boxer, Trafic/Vivaro/Primastar - those size vehicles with a higher payload.
As Gold says, if you run out of water half way through the day, it will start to cost you financially in lost business. If you run out of water at 2 o'clock in the Autumn, are you going to go back out for a hour after filling up? Doubt it.
The Maxi may look nice, it maybe economical to run, it maybe cheaper to buy, the neighbours won't complain etc etc, but if it won't do the job, it's a waste of money. Car salesmen appeal to your emotions when car buying - imagine the prestige driving this - head turner - when you drive this people will know you have arrived................................
Buying a van is nothing about this. Will it do the job we want it to do? - no. No point looking at it any further. Look at something that will.
Yes a bigger van will cost more and more to run, but it not always about this.
"An open cast mine had to replace a couple of 150 ton dump trucks, but they ended up buying a small fleet of 1/2 ton Nissan pickups instead. They sure saved themselves a lot of money."
My experience talking from years in the commerical sector of the motor trade.