u/jaccajjaccaj

I read this a number of years ago so it's probably at least 4 years old, I believe it was single POV, a character needed a fake date for a wedding and either he asked his roommate (maybe neighbour?) or his roommate offered, he might not have realised his roommate was gay. His roommate also had a low paying or maybe low prestige job of some sort but was (definitely unknown to MMC) secretly Very Rich. They were not best friends.

It may have been a novella or short story.