Bill slip for envelope for money orders or personal checks payment

[Tom Server]

My tenants were used to paying cash, since the property manger used to live near by and would go collect. Now I am the landlord and live 2 hours away and switching the payment to be mailed to me by money order or personal checks. Im dropping off pre stamped and addressed envelopes, which I know is much , but figured ill try to make this as easy as possible.  Does anyone use like a bill slip to add into the envelope ? something that has the month and they can write the amount they sent ?