Pet rats: adopting from shelter v. breeder and more

My first rat died a few months ago from an acute respiratory infection which developed within a matter of hours. We put him to sleep so he wouldn’t have to die drowning in his own lungs. He was a cloned albino lab rat that was a gift to us. He lived with us for about 20 months.

It was extremely painful losing him but now I’ve started to really want another. I’ll get a pair this time.

Two gray females and five males all a month old are up for adoption at the local animal shelter and I’m very tempted to rescue them but I’m afraid they’ll be more prone to an early death. I have no idea what their history or lineage is like. How much more dangerous is it to adopt a rat from the shelter than to buy from a private breeder?

What diseases/disorders are male rats more prone to? What about female rats?

Also, how much on average do you spend in vet bills for each of your rats?