Shades: I get this ALL the time. And you know what, just be humble and say it as is. You don't need to say "cause you don't have to pay rent bitch", no need to be embarrassed, just outright say it. Don't just say you're broke, but give examples saying "i just paid my insurance, I just paid my rent, I just ...."
I make way more money than my gf but she knows for a fact I have bills to pay and that I have rent and shit. IF the girl doesn't get you pay rent, fuck that, she's not worth your time.