You should read the FHA guidlines. There was an example where one 2 bedroom with a den was required to take 5 people and another 2 bedroom without a den was not. Reading through all the information given on FHA will give you a better idea what you should do.
In the meantime are you checking for credit scores? Are you checking they make 3x the income? How about savings. Now keep in mind that this criteria needs to stay the same for every one you interview but these are important screening points.