Families versus Groups of Unrelated Adults in SF Residence?

[Stephanie Jamgochian]

Hi! I'm a fairly new landlord.  I have a 4/2 Single Family Residence in a suburban neighborhood half a block away from a very desirable and highly ranked public elementary school.  My town is also a university town.  I've had mixed results with tenants: Tenant #1 was a dad with a toddler who broke his lease after he lost his job.  Timing was not great since it was in the fall, and the only applicants I had were groups of university students.  I leased the remainder of the year to four university students who despite the fact that I had gutted the house and almost everything was redone and was pretty clear on the house rules, has pretty much never cleaned the house and it's filthy (after doing the inspection).  They are not renewing their lease anyway.  I'm in the process of trying to find new tenants, but overwhelmingly, I keep getting groups of unrelated people-mostly 4-5 university students, some graduate students, or newly graduated/still in college.  I'm really hesitant to rent to groups of unrelated people as I just don't think they have the vested interest in keeping the house and tend to be harder in general, on properties (I have a couple of landlord friends who rent properties close to the university and they confirmed that students tend to be harder on properties).  

So my question is this: how do I attract more family groups rather than unrelated adult groups that tend to turn over more quickly? Any suggestions you have would be appreciated, or any insight.  Maybe it doesn't even matter? 

Also, can I legally limit the number of unrelated people (say to three) that live in the house? There are no local zoning laws on this particular matter.

I should also add that the rental inventory is extremely low and the vacancy rate hovers around 3%.