1.) you need to get two rats. No question asked, TWO rats. Rats are thee most social animals ever, especially males. They need to have that companion so at night when you're sleeping, and they're most active, they don't get lonely. Please please get two rats. 2.) I have a dumbo and three fancy rats. In my experience one is not better than the other, the dumbo has cuter ears, but that's about it. Also, it's part of the dumbo rat personality to be more calm, but they are also more independent. That doesn't mean they're not going to love you, they will, just less than a fancy rat would. Which can get frustrating. 3.) You will be able to tell if it's a male or female by looking at it. Male rats have..very pronounced parts by their tales. Also, most places don't cage females and males together. So yes, they should be able to sex them, and if they can't, run! That pet store doesn't know what they're doing!! 4.) No, not all rats have red eyes. "Albino" rats have red eyes. Typically with red eyed rats, they have poorer eye site, and they will sway back and fourth to decided how far away something is that they're looking it. It's cute! But if you have a red eyed rat and it does that, that's why. 5.) Yes, you can! I am currently. I have my dumbo, Rufus caging with my fancy rat, Coby. They get along great. Of course you have to introduce them to teach other first and make sure they get along, but if their young this should be NO problem at all. 6.) You CAN house two males toghether, I'm not quite sure why you think you can't... I have four rats, in two cages. They are all males living with other males. If you get them young, then it's not a problem, but if you put two males togethers and they bite each other bottoms or get puffy around each other, their just declaring dominance, and they have to do that, just don't let them get to carried away. Like i said though, young rats should not have this problem at all. Also if you can't decide which gender to get heres some tips Male rats are much more dependent on you. They NEED your love and affection for at least an hour a day, or else they WILL get depressed. They are much more likely to fall asleep on you and want you to play with them. They WILL miss you! Female rats get tumors, unless you fix them, and they can get several during their life span. They are just as friendly but dont' require you're attention like a male and they are more independent. So it really just depends of what you want. A rat that absolutely needs your attention and loves to be around you or A Rat that needs you but is much more independent.