The ACS variable OWNERSHP is a household level variable. The variable indicates if the dwelling the household lives in is owned by anyone in the household. The text from the 2022 ACS questionnaire is:
Is this house, apartment, or mobile home
-Owned by you or someone in this household with a mortgage or loan?
-Owned by you or someone in this household free and clear (without a mortgage or loan)?
-Rented?
-Occupied without payment of rent?
Each household member has the same value of OWNERSHP which refers to the same dwelling. The variable does not indicate which household member(s) are the legal owners of the dwelling. Using OWNERSHP, you can calculate the share of households that own the dwelling they reside in, but you cannot calculate the share of individual people who own a home. Filtering to PERNUM=1 ensures that only one member of each household is counted (in order to not count a dwelling more than once).