My two cents for the OP.
Housing
Even with pets, I say large tubs are the way to go. It's far more rewarding to buy a
90qt tub, cut out pieces of plastic and glue on screen for ventilation, and make it your own to buy an over priced piece of metal. Tubs also allow for LOTS of room, unlike even multiple stories cages. A 90qt bin, like in that picture, holds 5-6 adult females comfortably, and about 4 or 5 males comfortably.
Diet
For pets, just about any sort of rat/mouse diet will work. You want 15-20% protein and low fat, no higher than around 5%. The rules for any food is that it has NO dyes whatsoever, doesn't have a lot of seeds or is a very varied mix (rats WILL find a favorite tasting bit and eat nothing but that), and has no alfalfa or Timothy hay (only a little if it must have some). I also give lots of treats/table scraps. My breeders love hard boiled eggs (don't allow non breeders to have too much yolk), broccoli (steamed), steamed rice, tortillas, peanuts, and granola.
Health
Just like any rodent, rats are prone to tumors. Feed them right and keep them healthy to keep these away.
Rats are susceptible to RIs and respiratory issues, so pick a bedding with little dust. Normal Carefresh is what I used for my pet boy a few years ago, but it didn't allow for making nests to sleep in or foraging because it was sort of chunky. I think aspen chips with carefresh would be great.
Interaction
All my rats are curious, and a few really love to be held. You want to pick a rat who doesn't mind being petted, doesn't shy away, and will act curious. One of those WILL turn out to be a great rat to walk around the house with on your shoulder. Both my current big breeder and my old pet rat from years back were like that when I got them, and both are absolutely amazing.
Temperament
Again, you want one like how I described. Males are somewhat lazier than females, but seem to enjoy handling the most. Females are pretty spunky and would rather explore than be held, though the two girls I raised from birth do like to occasionally get on my shoulders and just chill. Males are also thicker bodied, but I prefer them, even if they are twice the weight of a same age/size female and have giant testicles.
Males are also very tolerant. My females are kinda spazzy, and one doesn't even like to be touched really or she'll screech like you just tore her tail off.
Life Span
Average is 2.5-4 years or so, but healthy rats can live to be 5 or so. It depends on how well they're cared for and their lineage. However, I feel that their food and their owner's interaction is more important than anything else.
Also, my pet rat from years back was from a pet store, and he lived to be AT LEAST 5 years of age. While breeders probably have lines of long living rats, don't think they're the only way to get a good rat.
Best sex for single animal
Ha ha, that's very funny. Get 2 or 3, you won't regret it.
What physical size cage would we need for two females? I have some bird cages but they are not 3 story. It is like a 2 foot cube. What do they need to keep teeth healthy and not over grown?
Bigger the better. Females love to romp around when they have the space. Males do too, but they squeal pretty loud and sometimes it gets a bit rougher than with females.
Feeding hard foods is all you need to do to keep teeth short, but I recommend a tasty chew toy mounted on the wall, both for chewing and venting the chewing instinct.
Also are there any major differences in personality between the variations? Rex, Fancy, Dumbo, American Blue, African Soft, etc
No.
However, African Soft Furred rats aren't even the same species. Stay away from those unless you have a local breeder nearby who will let you come by every day or few from the moment they have babies and let you play with them until you can take them home. ASFs are freaky things.
