What are reasons I can give to rescue over new puppy?

Well, call around at the shelters, puppies aren't hard to find at shelters. So maybe you can both have your way. Also, there are hundreds of thousands of puppies in shelters that will be put down, by buying from a breeder they are just hurting the cause. And, adopting is A LOT cheaper.

There are pros and cons to this. We have 2 dogs a beagle/mix and a german shepherd mix and we adopted both. They both have some issues and it's going on 4 yrs for one and 3 on the other. We did puppy school so the gs could have more socialization with people and other pets. This past February we bought a full blooded GS and it's so different than the other 2 in many ways.

A storm comes and he doesn't care. The beagle has always been upset by storms the gs wasn't until lightning & thunder happened in our front yard (he lays on the love seat to look out the window). Now when a storm comes he hides underneath the coffee table which has always been his safe zone from day one.

I love our mutts and glad we have them but, seeing issues with we've had to overcome with them is a second thought since we have a pup that doesn't have issues except for being a puppy.

If they adopt then it needs to be a puppy at a very young age not 6 months or older unless it was given up for owners health reasons, moving, etc. and I would still be careful about that.

Gosh, you have no idea how many pups come into shelters! I work at a shelter & it seems like we get at least a new litter or two every other week. The litters come and go, so there's always a fresh "crop" of puppies. There's no reason he can't adopt and get a pup all in the same swoop; he can go to a shelter, adopt a pup, and that's all there is to it!

Any dog or puppy can be trained "the way you want" as long as you know how to train him/her.

Sometimes it may take adult dogs a little longer to catch on though....depending upon the dog mostly.