One other thing, personal hygiene and sanitation. Where is the van dweller going to take a leak or a dump? He might not always have time to go to the gym to do it. And I presume the van would be too small to install a private toilet? Yes, there are public toilets near parking lots, but not every HK car park has an easily accessible toilet nearby. And speaking of public toilets in HK, well...not all of them are shall we say...all that clean? OP might have second thoughts about using some of them.
And if it is a residential parking lot, would the owners and tenants there want a long-term van "resident" who gives off bad body odour all the time? I mean even if the van dweller takes a dump in a bag, he will need to dispose of that bag in the residential apartment trash can, would the residents appreciate the trash can smelling frequently of the dweller's dump? I would think not. Not to mention the heightened alert to sanitation after Covid. I don't think residents are going to tolerate that.