Guest Parking at a multifamily residence

[Sam Leon]

In a 4 plex (one 2BR unit and the other 3 units are 1BRs), where in the lease agreement I have explicitly stated parking allocation is one parking space allocation per bedroom.  Total there are only seven parking spaces.  Five spaces for the tenants' own vehicle and two for occasional guests.

I have not assigned parking spaces, never had the need to, the tenants were responsible and friendly to each other, until recently when I have a new tenant who seems to be taking advantage, by having a work vehicle in additional to a boy friend who parks his truck when he stays overnight which seems to be quite often.  Other tenants began to complain that when they had friends over there is never any guest space. 

In my lease I do have a definition of "occasional guest" as someone who stays less than 7 days in a calendar month.  But I am not sure I want to use that because first, I really can't be there to monitor if a BF is there more than 7 days in a month, and second, I really don't care how often the BF stays, it is the parking space congestion issue I need to resolve.

A casual conversation with the tenant resulting in her playing dumb..."who? me? no that's not my car, I don't know who's car it was, my BF? He's not even in town..."  I am not sure why someone would lie on very trivial stuff, I have her personal car's tag number on the lease agreement, and her application has her employer who's logo is on the work vehicle LOL.

I also have a clause in the lease which says I can assign parking if necessary even though right now the spaces are not assigned.  I am not sure assigning specific spaces for specific units will solve this issue.

I do have the tag numbers of all the "registered" vehicles, when they applied they are required to fill out a form which they say how many vehicles and their tags.  The form is then binded with the lease agreement.  Now I have seven spaces, I have the five registered tags, how do I find out which vehicle(s) do not belong so I have have them towed?  Of course without mistakenly towing the true guest vehicles, is there a way?