Hey everyone! I'm currently in search of a male yorkie to call my own (I am so excited!

) and have a quick question.
I have always known that puppies should not be sold/given to different families and taken away from its mom until they are at least about 2 or even 3 months old (right?)
Anyway, I have found a couple yorkie puppies for decent prices here (and it's pretty difficult finding a decent price here in southern california!!), but they are either 4 months old or 5 months old. I am hesitant to buy a puppy at this age because I have this thing about raising the puppy straight from when he is either 2 or 3 months. That's what I did with my previous dog. I guess I just feel like I can train them "from scratch" if you will, and wont have to try and get rid of any habits they may have picked up from their previous home. I feel like maybe by 4 or 5 months, they have already picked up habits and gotten used to their previous home/owners/habits, and it may be difficult to train them to do differently?
I'm just wondering if any of you feel this is true at this particular age (4-5months) or do I not have much to worry about? I know every puppy is different in training, I just don't know if there's a certain age where they're just used to their daily routine, and if you change it, it can take even a little longer for them to kick any of those "bad habits."
Hope this makes sense and I hope someone can help me out! Thanks so much!