That would depend on the pony and what kind of treatment it has had in the past. If you get the pony from a reputable rescue, they will have handled it enough to know and will be able to tell you of any bad habits they have discovered. If you are getting this pony for children, make sure the children and the pony are compatible before you spend the money. The rescue should also have evaluated the pony for level of training and be able to tell you.
For a first pony for children, I always preferred a gelding. A good childs pony is worth its weight in gold and I have had a few of them that you could trust to take care of any child on its back.
Best of luck! Just don't rush into anything, make sure the pony you get is what you really want. A rescue organization will let you visit the pony and spend time with it before you take it.
Mary