I purchased a house in June of 2021. In the first two months I rented it back to the previous sellers (part of the sale contract).
That's referred to as a leaseback since it was part of the sales contract. Generally, you just have to reduce your cost basis by the amount paid to you during the leaseback period. Nothing concerning this gets reported on SCH E or any other part of the tax return really.
The IRS has many views on this and it seems that it's dependent on the specifics of a given situation. To see what I mean, see https://nysba.org/NYSBA/Coursebooks/Fall%202018%20CLE%20Coursebooks/Commercial%20Real%20Estate%20Le... and read "all" of it. That is, if you can before your head starts swimming in a sea of confusion.
For your room rental, it's the percentage of square footage that is exclusive to the renter, based on total square footage of the structure.
