Existing tenants are harder, and you will not get all of them. Aim for the check-writers who are reliably late and the tenants who already pay by card at the counter every month; they benefit most and resist least. Leave the retiree who walks in with cash on the 1st alone.
Give each group one easy path. The tenant who is comfortable online gets a portal login where they save a card and switch autopay on themselves. The tenant who will never log in gets a payment link by text or email, pays once by card, and you ask at that moment whether you can keep the card for next month. Ask once, and record the answer either way.
SFC supports each path. Invite one tenant or a selection of tenants to the tenant portal by email; tenants sign in with their email and an access code, see their balance, pay by card, save a card and switch autopay on. For the tenant who will not log in, staff create a secure one-time payment link and copy it into a text or an email, and the tenant pays by card without logging in. When a tenant agrees on the phone, staff save the card and switch autopay on from the tenant's page. The dashboard shows how much of this month's scheduled rent is on autopay, the number to watch during the push.
Texting the offer works, but consent comes first: under US carrier rules a tenant has to opt in, every message has to identify the sender and say how to stop, and a STOP reply has to be honored. SFC records each tenant's texting consent, texts only opted-in tenants from a verified toll-free number with your facility name and opt-out instructions on every message, and will not text anyone who has replied STOP.