The key is to protect yourself. You do not want to be forced into a sale / bankruptcy here. This means some things:
1. Try to stay in town. Managing property remotely will increase your costs substantially.
2. Make sure you have a cash cushion.
3. Price your rental slightly low. This may not make sense at first, but here’s why: You CAN’T afford much vacancy or a bad tenant that damages your unit. By pricing slightly low and advertising right (and treating your tenant right) you will be able to select the best tenant you can, which minimizes the risk of: Bounced checks, disappearing tenants, damaged unit, etc. I’ve had all of them. And when you have > 20 units it’s part of life. YOU have all your eggs in one basket, so guard the basket! Good tenants are out there, but they have their choice of rentals and you must compete.