I think he meant rented warehouse space, not an actual storage unit. Storage units rarely have more than a single electrical outlet and many lower end ones don't even have that.

Most of the plumbing technology developed for RV 'boondocking' would be perfectly adequate. Bit of a PITA, but I've done that for 2.5 week stretches in the mountains on ~1 gallon/day of H2O. My real concern would be no windows, definitely not great for anyone who suffers from seasonal affective disorder.

Water tanks filled from outside and a composting toilet maybe?