Hi Cliff--
It sounds like you're trying to come up with the definition and criteria?
For sure, look at the income of each individual person in a household (or more limitedly: a family). That's going to be in the "P" table of ACS PUMS.
College enrollment status sort of makes sense... but is the college enrolled person a relative (usu. child) of the householder? or is she an unrelated housemate/roommate? In that latter case, that does not seem like a dependent relationship (though she may be dependent on family living entirely elsewhere -- and you won't have those characteristics in ACS PUMS.
Good luck!
--Todd Graham