In a nutshell, what you have is nothing more than a cost sharing arrangement. So there is absolutely nothing what-so-ever that needs to be reported on any tax return. Especially since the shared amount will be less than $15K in any one tax year.
You are creating unnecessary paperwork that "could" result in an audit years after you file, that could quite easily turn into that never-ending nightmare with the IRS from which you never awaken.
Since this room mate is the GF, this is 100% personal use, as I seriously doubt the occupants sleep in separate rooms and have their own separately designated "personal use" rooms/areas in the property.
