Welcome and congrats!
I am super glad to hear that you will be rescuing!
It would be perfectly alright for you to leave your puppy (in a puppy proofed area of course!) while you are at school or work, especially since your mom will be coming in the middle of the day for a potty break.
Here is some good info on crate training! https://www.dogforum.com/dog-training...ning-faq-3974/
There is also a lot of good information on other topics in the Puppy and Dog Training sections of the forum.
And just a few things to think about...
1.) Choose a puppy or dog based on energy level and temperament, not looks alone!
Make a "wish list" of characteristics so that shelters and rescues can help match you up with the right pup or dog.
It is far easier to life with a dog that fits your lifestyle rather than having to change your daily routine to keep a dog happy.
2.) If you are worried at all about house training, check out adult dogs that have already been house trained.This may actually be a good idea since you are going to be at school during the day. (Just something to think about!) Also, an added bonus with adults is that they have already matured, so you will know their energy level and temperament.