ooo, we love rats

he does look rather young, he may like to ride around in your top pocket (remember to line the pocket, or use a lab coat or something washable)
he'll get used to being handled, all the rats we have owned have been very smart, they like to sleep in the bed with you too & cuddle

also he will toilet train himself, he will pick a corner to use & after he decides which corner, you supply the toileting surface

have fun & make sure your tetanus shots are up to date, lol.