How Do I Start A Successful Retail Business?

I need assistance to get my questions answered regarding starting a retail business:
1. Which retail business would be best to start and why: a) Specialty retail business or b) Mail order business?
2. Which type of business is more predictable and does not change often: Specialty retail or mail order?
3. Many people say that PASSION is important when it comes to starting a business because the owner will have to work long hour to make his or her business a success. I agree with that but can you explain to me why there are many people out there who started their successful businesses outside their PASSION?
4. How can I choose products and services to sell that fit my personality and are part of my values?
5. I took a Myers-Briggs personality test and the result of the test shows that my personality type is an ISFJ (Introverted, Sensing, Feeling, Judging). Would someone like me who possess this personality type can become successful in operating his or her retail business?