What do I have to consider or take note of before I adopt/buy a puppies?

As mention above, what do I need to consider? As I wish I can find a puppy to adopt, because I'm staying in HDB flat & I'm quite afraid of big dogs. I like puppies, & I don't have problem with puppies. But when I was small, I got chased by a big dog. So till now I still got phobia of large breed dogs. So if possible I wish I can adopt mini maltese, yorkshine terrier or maybe shih tzu.

My house have kids(my sis... & cousins when they come on weekend), so if I wanna have a puppy I must make sure it can play with the kids & not hurt them.

I want a puppy because I want the puppy to accompany me for years. If adopt adult dog like 8yrs old, then I'll only left with 3-5yrs with it. I want to see it grow. I want a puppy around 2-3 mths old. If I'm not wrong, puppy can not leave their parents too early. Not younger than 8weeks.

But I'm still not sure about how much they eat per meal, bath how many time/day per week, how much is the mircochip & sterilise & licence thingy, and others that may be important. How much Do I need to prepare for a dog's need & compulsory things?

This is the first time I'm adopting a dog. So I don't really know much. But I can promise I'll take good care of it. So I need to find out more before I adopt it. I'll try to adopt but if I really can't find maybe I'll buy.