Mother in nursing home; had joint account for ten years with her. Nursing home said I can take $500 gift each month. Is this true?

If your mother is receiving Medicaid, she is regarded as having access to 100% of the joint account.  That money should all go to her care.  Any gift (and this could well be seen as a gift) of $200 or more in the five years before she applies for Medicaid could disqualify her for a certain period of time.  You might do well to consult with an elder lawyer.  You can find one near you on the website of the National Academy of Elder Law Attorneys (www.naela.org).