Tenants are equally responsible for observance of the by-laws as owners. Why would you have a lease condition requiring only so many car owners to live there, when they may be doing the right thing and parking their car in a legitimate place, ie not in a visitor car space? Anyhow they may not be car owners as such, having leased or borrowed the vehicle, and then parking in the visitor space. You’re also asking a bit much of the selling agent as well to determine whether prospective tenants are telling porkies about the number of vehicles they intend to bring with them.
Though I did once jump on a real estate agent who was advertising “additional parking” with a unit, which only had a single garage. I told him in no uncertain terms that the visitor parking on common property was not part of the title being sold therefore he must remove the reference from the advertisement. The unit he was selling was no different to any other in the complex, it had no additional allocated car parking.
Legitimate car spaces are shown on the strata plan as part of the lot, but how many cars the owners or tenants have at the beginning of their occupancy should have no bearing for the reasons above. In any case what is to stop them acquiring more vehicles after they take up occupancy under your suggestion?
regards
Dave B