How to go about telling a tenant rent will be raised

[Wences Lopez]

I bought my first investment property in August, and let the seller stay and be my tenant for 3 months until he bought another property. He hasn’t had any luck buying anything. Current rent i charge him is $975, basically just paying my mortgage for now. Rents around the area are around $1375-$1550. What’s one way I can tell him Im planning to raise rent?

(Reason why I let him stay at the mortgage rent price was cause he fixed all issues that came back after the inspection, around $6k in expenses & sold me it at the price we first agreed on)