I need help with a personal care agreement.

I have been taking care of my sister, 71, for six months. We were roommates and still are. She is in Hospice care, so some of her needs are met by this, but I basically do everything else. There are no other family members to assist in any way. I handle her finances now, and I've been paying myself a monthly fee. She also pays for household expenses, which we previously shared equally. I have just learned of the Personal Care Agreement, and I think I'm six months too late? Shall I do one now, and hope for the best with Medicaid (California) down the road? Must it be notarized? Maybe it could just be witnessed by two non-family adults? My sister cannot leave the house, so I'd have to pay a Notary to come over, if this is required. Neither one of us has much money to spare, although she's got quite a bit more than me. I'm muddling along... any advice would be most welcome.