What happens if my rental cost less than others?

not sure of the question you asking, but to be able to properly report rental real estate activity. any day rented to anyone at less than fair rental value is considered a personal-use day. Days rented to family members are personal-use days unless fair rent is charged and the unit is the family member's principal residence. IRC 280A(d)(3)

however, a taxpayer were able to win their case when charging less than fair rental with the court allowing a 20% discount because the tenants were the taxpayer's parents and were expected to take unusually good careof the property and management fees were avoided.