well if you feel that a pup that is already housebroken is better, than i'd go with that.
Also, bear in mind, dog's tend to sense our feelings. If your new pup sense your mom is upset about the accident it may make it more difficult for the pup to be housebroken.
Getting a dog that is already housebroken takes away alot of the stress that comes with a new dog.
Researching is great but it doesn't prepare you well enough. If you choose to get a puppy (6 months or less) then you will need to have LOTS of patience. There will be potty accidents, biting, chewing, etc. that will need to be dealt with properly. Crate training is great BUT you cannot leave a dog in the crate for extended periods of time. They require lots of exercise & consistency. I have had puppies & I've adopted dogs 3-4 yrs old so I've seen 1st hand the good & bad of both. Dogs required a lot of your time regardless of their age & requires EVERYONE in the family to be on board with training otherwise there will be problems. Having a dog is next to having children, you have to make sure they are cared for if you go away & can't take them with you, they need your attention daily or there will be issues. I LOVE dogs & I wouldn't trade mine for anything, my little foster who was 3-4 months when I found her has reminded me why I don't want a puppy again. If I ever get another dog, they will be at a minimum 6 months old, preferably over a year. Sorry, just had to throw my 2 cents in, I've known some very well intentioned people who did not do well with a dog because they didn't realize a dog required so much work & money.
Some puppies are worse than others to toilet train. I heard toy breeds can be difficult as their bladder is so small that it takes them a while to be able to hold for long periods.
Only trouble with bigger puppies is that when they do have an accident, it tends to be a lot bigger. Having had three German shepherds in a relatively short space of time, the whole idea of puppyhood makes me shudder.
We crate train all our puppies now. Never use to, but crate training makes life so much easier. You just can't get lazy with crate training and let your puppy learn to foul in the crate otherwise you have just defeated the purpose of using the crate.
If you think you aren't going to be able to cope with toilet training or that your mum is going to freak out, maybe look at an older dog. The worst thing you can do is to scold a puppy for having an accident. Our 14 month old used to hate when she had an accident and she would run and sit by the door, so freaking out would have been completely the wrong thing to do.
Other than that, really the only reason I would get a puppy is because that way I can control its training and upbringing. I know every single trigger for our dogs, and how to handle them in almost every situation.
I have seen the results of bad handling and training in two of the dogs we have gotten from the RSPCA, which is one of the reasons I prefer to start from scratch with a puppy.
The two dogs we have right now really weren't that hard to potty train, but then we spend a ton of time in the back yard with them and gave training treats when they would potty outside. Thankfully we have wood and tile floors so the few accidents we did have were easier to clean up.
I've got all the time in the world. Lol I have no social life. I think I have enough patience to train a puppy and I would never leave my puppy in a crate 8 hours straight. I had a neighbor who did that with her bichon Frise and the dog developed all kinds of bladder problems and had to have surgery twice. My neighbor also let her dog have bread, candy, beer and hamburger.