benefit buddy

Similar to friends with benefits; However the people involve, while friendly, are not usually friends. Either socially, academically, or professionally they are typically casual associates or acquaintances.

Where 'friends with benefits' are typically friends in addition/prior to sexual gratification, benefit buddies remain 'on-call' for sexual gratification, but typically avoid all other forms of contact if it can be avoided

My math tutor is my benefit buddy; He's shows me math, and I show him my bedroom. Other than that we don't associate.