As you apparently know, because he has no taxable income, you can claim him as a dependent if you provided more than half his support for the year.
The $45,000 is support you provided. The $40,000 from loans is support not provided by you (unless you co-signed the loan). If that $85,00 constituted all his support, you can claim him as a dependent.
If there was other support, The IRS has a worksheet that
can be used to help with the support calculation. See: http://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
If the student lives at home, you may count that as support. He is still considered as living at home, if your home is his principal residence and he is temporarily away at school. The support
value of a home is the fair market rental value, divided by the number of
occupants.
