Community Associations Institute (CAI), a US-nationwide
organization that caters to common interest communities -- HOAs,
condominium associations and co-ops -- publishes that 70,000,000
Americans own this kind of real estate. That's about 21% of the
population of 318,900,000 (2014).
They do not tease out the different styles of ownership in order
to give you a specific number for HOAs.