Tax Help PLEASE! How do I file income on rental property for property I don't own?

I am a self-employed psychotherapist.  I lease a suite of offices from a property owner.  I lease each office out to another practitioner.  I make a small amount of money from doing this. I can't find a place to put this on my taxes.  If I put it in Rentals and Royalties and state that I own 0% of the property the income does not seem to show up as taxable income...which is GREAT if I don't have to actually pay taxes on that income but somehow I doubt that is the case.  Anyone, anyone??