I love rats. We kept up to 30 rats at a time in large bird aviaries when I was in my teens. After seven years my Dad developed an allergy to their urine and we had to stop keeping them.
Historians are now starting to accept as a fact that rats did not cause or carry the plague as far as it went; people did.
Out of the two things I learned in History, one being that rats carried the black plague and the other being that World War II ended in 1945, you want me to believe one of those is false? Then I'll be a complete nobody in terms of historical knowledge. :/
Rodents as pets are adorable, especially with long tails, like mice, rats and gerbils.
The only issue I can think of presently with getting a rodent as a pet for a kid is that they can be cannibalistic in certain situations. My friend had three pet rats, and I believe one of them got sick, so the other two ate him. This friend seemed extremely disturbed, and his little brother probably was/would have been too if he saw that. But yeah. I've never experienced this with my pets nor anyone else who I knew had rodents for pets.