Your post is vague, and appears to be about two unrelated subjects. Rental income, and dependents. (Daughter moved back in, and cousin makes $25/hr - how do the two relate to taxes, if they relate at all?)
Did she rent out an entire home? Or was she just renting out a room in her primary residence?
"head of household taxes (my aunts)?"
So your aunt has a dependent that qualifies her to file HOH?
Deal with the rent stuff first.
" She wouldn’t be profiting at all"
I doubt that. The major deductions here (but not only deductions) for rental property is property insurance, property taxes and mortgage interest. The principle part of the mortgage payment is never deductible and is taxable income to the owner. But this is usually offset by the depreciation that the property owner is legally required to take. So lets deal with the rental only for now.
- Was the entire property rented out? Or only part of her primary residence?
- Was it rented to a related party that is related to your aunt? If so, what's the relationship here?
- You mention being rented at below FMRV. How are you determining that it's rented below it's fair market rental value? That matters, because that figure is *highly* subjective and most incorrectly assume they are renting below FMRV when it fact, they are not.