I've only had a little experience in that I would have one of my Sims purchase one of my Business Creations - (Retail of course); have them stock it and then sell the business (and not to anyone really) - this is so my Sim could do other things while the business (Retail) would take care of itself.
So this challenge is to purchase a business - (retail), stock it and run it.
I think I would start this one early. Even toddler stage would not hurt, then as a child - have the sim be a social butterfly; as a teen the child could get a job in either retail or fast food - (or have several teens and one in each type of business for their part time job).
As a young adult:
So - Open your first business would be number 1 goal on the list.
Build the skills your Sim will need for that business - whether you chose a restaurant, a coffee shop, a pastry shop, a clothing store, or all of them, whatever - it will require skills to furnish better product and do well in that chosen business. In addition -
Build your Sim's Charisma skill to top level
Build your Sim's Mechanical skill to top level
Earn a lot of money - The Sim should want to be rich and his/her interest in wealth is a given.
It might be fun to do this for each type of business. You could have several sims with each running a business at the same time (that would give you several businesses. It would be a competition between the sims. See which ones are successful, and which ones are not).
