If so how do you sort out gear storage/water production?
Yes, I'm in a flat.
I rent a place several miles away to do my filtering and store my stuff.
Well, you did ask

.
It wouldn't be practical to do it here. I can't even be sure that I can park in the same street as were I live, never mind being able to get close enough to transfer water.
One thing I did consider - and might have tried if I hadn't found an alternative - would have been to pay the water company to fill from their hydrants. With a very fast RO in the van it may have been feasible.
I even considered getting a much larger van and having a twin tank system. Fast fill tank 1 from mains. Pump water from tank 1 to tank 2 through RO. I'm sure it could be done with a bit of forethought - even while driving. Waste would need to be stored temporaRILY AND DUMPED OF COURSE. It would need split chargers and several leisure batteries so that they could be swapped for manual charging.
Complex, so it would need to be planned well.