My primary residence is a duplex. Tax question for the rent paid by upstairs tenant

[Cody Lown]

Hi all,

I purchased a two-unit home a few years ago as my primary residence with a conventional loan, and was told by an accountant that there is no reporting or extra tax forms I need to file as long as my tenant in the upstairs unit is paying less than the total of my mortgage. The more I learn, the more I think they may not be the case, and I'm curious if I need to go back and amend any taxes from previous years to ensure I am following all regulations.

The details:

-two-unit home that was converted from a SFH by a previous owner.

-both units share the same address. I have had an internet provider require me to specify "Upr" or "lwr", but in general, just the one number.

-the tenant is a friend of mine, and I believe his car and address for employment and bills is still listed at his parents' house a few cities over. 

-he pays $550 of the $930 mortgage, and half of the utilities, which are not split, and are in my name. 

am I overreacting, or do I need to do some damage control on the tax front?