If I have a specific story in mind then I will create the sims or family that I need for the story and using Nraas mods I will build the characters to reflect them in the story. In other words, my founders will have the traits and skills needed as if they have been in the world for the length of time the backstory determines. I don't start them all at zero. Only sims born in game start at zero. I add new sims periodically for marriage or to add a new direction for the story to go. I don't use EA sims, they are background sims. They can be friends, but not relations. :) I either make my own sims or steal err...borrow from friends studios. :lol:
If I am doing a rags to riches type story I will start with one or two sims and they do start with zero skills and zero finances based on their back story. I usually allow them to dumpster dive for items to sell or put on the lot to use, pick flowers, seeds, rocks, bugs etc to sell, and as they learn skills they can then earn money with the skills. They can get a part time job once they have a small home built on the lot, but, if they get the part time job, no more collecting. Careers require at least half of a needed skill to be learned before they can enter a career. Those are my own rules and I also have a rule that I can change rules at will. :)
Right now I'm trying to have a long running story with connected worlds like @igazor so I can play various members of the family or their friends as the story develops.