Pet/fancy rats have gone through some breeding selection to try and weed out aggressive behavior (or at least bites). With that said, a wildie can be just as friendly, but you'll want to be extra careful to try and curb negative behaviors.
You can raise a baby rat (although it doesn't need to be a baby, too) found in the wild, because they are virtually the same as domesticated ones. At least here in Europe, where I live.
The type of a rat you're looking for is a "Norwegian Rat" or "Brown Rat", which is the most common type in the wild.
Generally speaking, there's a saying that animal you rescued will try to pay that back in love.
If you're somewhere that rats are native then you should leave them be, if the choice is between killing them to protect our native species or keeping them in nice conditions until they die of old age then I'd hardly call it kidnapping!