I had rats as a kid. My mother was very tolerant.
When I was a kid I didn't know this... rats are incontinent. They pee constantly. You can't see it until you shine florescent light on it. I know it is true of wild rats, but I am not positive about the pet ones.
You might want to look into it before you let him crawl around on you before work. Had my mother known about this I would have not been allowed a rat as a pet.