Key: take a look of their finances

For people in hard-to-find-tenant area don't just reject tenant application because of number of people.  Take a look of their financials: how many are employed and how much are they making?  They have better be making three times of monthly rent amount.  If that is a yes then go ahead and ask for 1.5 or 2 times of security deposit citing over-crowd concerns.  Negotiate and get >1 month deposit.  Don't forget to get a pet deposit if applicable.  Also remember to put on a standard (preprinted) lease agreement.  No short-cuts.