Resources are anything that can be converted to cash to pay for care. There are exemptions that apply to a narrow scope of resources. But otherwise, anything that doesn’t fall into an exemption is subject to spend-down.

Does the cash under the mattress count?

Yes, it does. Many people have assets that are “off-the grid.” But this doesn’t change your obligation to report these assets to Medicaid and they count for eligibility. A failure to disclose off-the-grid assets subjects the applicant to the possibility of criminal prosecution for Medicaid Fraud, which can be a felony.