Well fisrt off, I had a dog as a teenager and I was useless then too!
Secondly, I would go out and buy some books, and study up on toilet training and basic obedience waaay before getting a dog, from a very young age I was obsessed with dogs and always got books on dogs out the library and when I started getting book tokens I bought dog books. The best ones I would say are Gwen Bailey's The Perfect Puppy, and a book called Everything you need to know about dog training.
Why don't you go along to local dog classes and see how other people are around their dogs? Do you have any friends with dogs you can help out with, like walking, or anything?
If socialised properly around children from an early age, a dog will grow up with your con and they will be firm friends, provided you set boundaries- like never letting your son poke or pull the puppy, or ever going in its bed, and always give the puppy a clear way to his bed incase he's had enough.
Look into dog sitters or kennels, there are many various places and prices, and they will care for your dog when you go on holliday
As long as you get the puppy used to being in a different room to you sometimes, you should have no problem leaving it at home on occasion.
Also, take advice from people who know about dogs which breeds would be best for a ''first time'' owner with a young child. I am thinking along the lines of golden retreiver, labrador, cavalier king charles spaniel.
Greyhounds are also great if you were to consider a rescue, most of them are good with children, and you can get ones that are cat safe. An older dog might already be toilet trained/partly trained in other areas too.
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