urgent help needed!!!

i am looking for a roommate and i put an ad in the internet and i received an email asking for more details. i sent out my address and phone number and i received a reply saying he is a gay!!! i am not comfortable to have a gay as my roommate but i am not sure how to reply. is it against us law to turn him down just because he is a gay? gurus, please help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!