If my parents write me a check of $ 500 a month to help continue to care for them at home, does this need to be reported to IRS?

Yes, because it will count as your income which I believe you will have to claim on your taxes, and their health care and their taxes. I suggest you talk to an elder attorney before starting this. He will give you suggestions, and can draw up a contract stating that such payment was for this - because if your parents wind up needing to eventually go on Medicaid - it will not be counted in the 5 year look-back requirement. Good luck!!