I've lived with a female friend before - twice actually - and here's what I've found: they are GREAT to have around.
Why? Social proof and jealousy, both of which are GREAT for getting OTHER girls to sleep with you. If you're dating someone and you take her back to your apartment... and they see that a girl is living with you and she's even marginally attractive, the girl you're on a date with is more likely to have sex with you.
The girls you're dating don't like to think you only hang out with ugly-to-average looking women 'cause then they'll think they're also in that category (strange logic, I know). However, if you have a hot-looking girl as your roommate, they'll believe that you only hang out with hot girls.
At the same time, they'll also ponder if you and your roommate have ever had sex before. "If his roommate is so hot, how could he NOT have banged her?" will be the thought going through her head. Then, if you tell her you haven't banged her before, she starts calculating the odds that you MIGHT bang her in the future... unless SHE gets to you first.
And thus, your girl roommate will actually help you get laid faster just by being the head game in your date's head that moves her to sleep with you faster.
Now, this could just be my reality, and i'm sure people on here may disagree with what I've just said. All I know is, every time I've even mentioned having a girl roommate - which I would usually do on the first date 'cause they'd ask me - I was able to bang the girl by date #2.
So, don't try to bang your roommate, but definitely use her to help you bang other girls
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