I've had over 40+ rats since starting my love affair with them. I only have three right now, but at one point I had two huge Martin cages and 14 girls and boys at once, WITH two other large ferret cages for when I had Rex babies or a nursing mum that was separated from her sisters. They are the funnest creatures, and if you can't have a dog, a good stand in. Mine are all litter trained, know their name, and sleep in a bird cage with homemade fleece hammocks for levels and fun!
I use carefresh, the one without dyes or added absorbency and only use a tiny amount in their litter box. I change it twice a week and wash their bedding every 4 days, but I have tons of sets so its quite fun to change it around and have different fabrics. The rats love the change as well, on top of that they recycle all my cardboard boxes and other cardboard things. Mine roam the house and aren't much for chewing, but DO find their way into my pantry loud enough for me to notice and get them.
They get fed our food and a homemade grain mix that focuses on their protein intake(not high), vitamins, and actual grains. They get a high grade dog food, Taste of the Wild, but that's SO small. They get bits of our dinner if they beg good enough. :p
I've had to spend 300+ dollars on rats, tumor removals and spays being the highest costing. So having a pet budget is crucial because if their lines aren't healthy, you basically get a kid that gets sick easily. And they decline QUICK. :c (My latest deceased is Frappe, my sweet coffeebean had just gotten a tumor removal not 1 month before, and catches pneumonia that quickly took her despite medication and treatment. :< )
But rats are great and come in a unique assortment of colors and ear sets. Boys are rather chill and wanna hang out while girls want to explore the whole world, but still give kisses and get treats. Mine roam the house, get baths, and know tricks. smile (Spin, Kisses, Come see me, one even knew how to pick pocket.)