There are 'mathematical' minimums and psychological minimums. Although not the smallest living units by any means, Architects pursued the idea of 'existenzminimum' during the 20s and 30s. This was not confined to floor area, however, as it sought to determine the minimum sunlight, ventilation and open space needed for a dwelling. The approach, however, was 'scientific' or objective. Pod or capsule dwellings become popular every so often with architects and are based around aircraft like designs of interiors with everything needed built or moulded into floors, walls and ceilings. These can be as small as 32sq.ft. or 3.2sq.m. These are functionally possible but one has to question how long one can live in such a small area without suffering in some way. J.J.P. Oud's Weissenhof existenzminum design for 2-1/2 bedrooms are 1260s.f. (126s.m.) plus garden.
Psychologically or experientially, minimums are up for debate. The recent series 'The Secret Life of Buildings' by Tom Dykhoff demonstrated the negative effects of small spaces, poor lighting conditions and so on. The UK averages 760s.f (76s.m.) compared to Denmark’s 1360s.f. (136s.m.). In the 1960s and 1970s U.K. housing sizes were controlled by the Parker Morris standards. These did not, however, determine minimum sizes, but key clearances and provision, such as storage space. These standards, based on research into the lifestyle changes that had taken place since the 1940s (cheap electronics and plastics = more gadgets, therefore more storage, or more time spent in front of the television, or taking dinner in the kitchen) tried to ensure that units were suitable for contemporary life.
The Parker Morris standards are now considered extravagant and most private housing is built to lesser space standards than the public housing built in the 1960s and 1970s. Tenants and owners tend to praise the units, and they are highly sought after in the private market.
It would be interesting to carry out new research around contemporary lifestyles and come up with new Parker Morris standards that were not about area minimums, but about the minimum requirements for a (mentally and physically) healthy and comfortable life.
Obviously; one can also bring into the equation from a minimalist standpoint the fact that prison cells in the US penitentiary system have been deemed to be physical & psychological Humanitarian minimums for necessary space.
And the above is a measure & information principally describing building types but RV are only buildings with wheels so a correlation is justifiable especially when one is talking about someone who is living by choice as an un incarcerated individual.
Ultimately for a person that I assume is not incarcerated; it is your choice and only yours as to how, where & why you want to live and someone else's choice & opinion of lifestyle is really meaningless as to what will work for you........
INTJohn