I would wait till they are at least a year old, that way you can give them a very strong foundation giving them 100% of your time. Having a 6 month old pup and a 8 week old pup will be very hard on you! That would be my suggestion.
As for the multiple dogs.. I think it depends on the owner and dog. I feel very torn on it myself. Zelda loves other dogs, but i think our relationship with take a step back if i got another dog, but maybe it would be worth it, especially if i got a dog from a kill shelter or something, that i could save and than Zelda has a buddy when i am at work, etc.
But i know dog people who have more than four dogs, and their dogs are all very happy and just love no other like they do their owner!
So maybe with time, you can figure out how much your dog depends on you, likes other dogs, if you still feel the same way in a year, etc.
More money, more food, more vet bills, more time.
When your gone, they have a each other, that is if they get along
You can give not just one dog a good home, but two dogs a good home.
Plenty of negative and positive.
It boils down to individually what is best for you, your dog and your current situation.