I am relying on my memory of books that I never supposedly read, but I did. See, in the 1960's and 70's, boys were not supposed to read Nancy Drew--boys read the Hardy Boys series. But, I would sneak and read Nancy Drew because they really were about the same as Hardy Boys.
Nancy Drew solves mysteries and just like the Hardy Boys, these are situations that Nancy just finds herself in- she is not hired to solve the cases. I presume she gets all of her money from her father, a well-respected attorney. Like many fictional characters, Nancy never seems to age and is always about 16, 17 or 18--same with the Hardy boys- one was always 18 - one was 17.