My mother is like this. She rents out her house for under half it's market value.

The tenants know they have it good though and do a lot of things that really should be my mother's responsibility like pay for or do minor repairs when they come up.

I have told my mom that the needs to raise rent at least some because she's not saving enough for big things that will come up like roof replacement, but she's terrified of her tenants leaving.