What Are the Tax Implications of Leasing a House for Less Then the Mortgage Payment if Any?

mortgage

I want to sell the house, but don’t reckon it is doable with current market. Also, 1 house has been on sale for 6 months with only 1 interested person. There are 4 houses that are lease houses, not sure the $$ for each to lease. I was going to lease to my mother-in-law to be for smaller amount than what mortgage is currently.