I left home on June 6th and before joining, the only expense of mine I did not pay was rent. I paid for all of my other bills (phone, food, gas, car payment/insurance, etc.) rarely stayed or slept at home, and was not a student.
A lot depends on your age. There are two types of dependency tests, one for a "child" and one for relative. I will include both. Support might be the main issue here. It is worded differently for both tests, but you will still have to accurately account for every dollar spent for support from othe sides.
https://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
In general, to be a taxpayer’s qualifying child, a person must satisfy four tests:
Relationship — the taxpayer’s child or stepchild (whether by blood or adoption), foster child, sibling or step-sibling, or a descendant of one of these.
Residence — has the same principal residence as the taxpayer for more than half the tax year. Exceptions apply, in certain cases, for children of divorced or separated parents, kidnapped children, temporary absences, and for children who were born or died during the year.
Age — must be under the age of 19 at the end of the tax year, or under the age of 24 if a full-time student for at least five months of the year, or be permanently and totally disabled at any time during the year.
Support — did not provide more than one-half of his/her own support for the year
Qualifying Relative.