When student veterans are apartment-hunting, they often find themselves having to show "proof" of their GI Bill housing allowance. The best supporting document: your enrollment and payment verification letter.
What letter, you ask?

At the start of each academic term, once your VA enrollment certification has been submitted and processed, the VA mails you a letter that verifies the information that the school submitted on your behalf, including the start and end of the term, how many credits you're enrolled in and your net tuition and fee charges. You should always double-check these numbers to make sure they are correct, and let your school certifying official know if there are any discrepancies.
The letter also says how much the VA will pay you in tuition/fee benefits, book & supply stipend, and monthly housing allowance until the end of the term, and then tells you how much entitlement you will have remaining when the term is over.
Your term verification letter is an important document that you should file carefully - don't just toss it aside. If you haven't been getting your letters, call the VA - you might need to update your mailing address.