Many people whom I knew growing up cared for hamsters as their "starter" pets, which while not inherently bad in any manner, always seemed more detached to human contact from my experience. After the angry, senile hamster whom I rescued from my childhood friend passed away, I decided to move on to rats.
Since reading the book "The Secret of NIHM", I was highly interested in rats and for what reason they were often treated as dirty or scary, even when bred specifically to be pets. I began researching rats as a species and as a domesticated animal, and after falling in love with their apparent intelligence and curious personalities, I began to care for a pair of rats with my sister. We affectionately named them Justin and Nicodemus.
The rat which I primarily took care of, Justin, was incredibly smart and eager to please. He was potty-trained faster than any cat or dog that my family had owned prior, and learned to come when his name was called after a few weeks of positive reinforcement training. For the most part, he kept himself clean; rats are meticulous about the oils which they allow to come into contact with their skin, and seem to have an aversion to human oils (they will clean themselves after you are done handling them). Justin got along very well with Nicodemus, although they squabbled from time to time, and probably would not have lasted as long as he did if it weren't for his companion. Although he was an amazing animal to have, I highly regret purchasing my rats from a pet store.
The pet store fancy rats are NOT bred for their health. The two we purchased were no different. Justin and Nicodemus only lived three and four years. Justin passed away first after he suffered a stroke which paralyzed his right side. He struggled for a month with eating and had to be provided with ground-up meals before he finally passed away. Nicodemus became afflicted with a cancerous tumor and was euthanized shortly afterwards.
Because rat care is relatively simple, and even the healthiest of rats don't live very long, I would recommend these affectionate animals to younger people. However, I would not recommend them to children who have yet to develop a sense of responsibility because they are fragile and need to have their cages cleaned often in order to keep the room that they are housed in from smelling like feces.
If I were to get a rat again, I would definitely look into local breeders in my area, or rats in need of rescue from the local animal sanctuary. It is also worth looking into amicable housing requirements for rats outside of pet stores, because oftentimes the stores will recommend cheap housing suitable for smaller animals such as mice and hamsters (which rats will not fare well in). Rats do best in pairs, as they are very social, and seem eager to accept their human friends into their makeshift colony.