If you can give 20 hours per week of organized-focused time you can build a successful small business. Why do I know this because I have done it quite a few times. My suggestion is to start a service business. For one your not chained to store hours and most of the responsibilities can be hired and quickly.
For one you can hire an answering service to field all your calls and for a little extra even do basic scheduling.
If you follow my rules of picking a service company which is one that you can hire the skill needed (mowing, gutter cleaning, etc) with a simple classified ad in 2 days or less. With craigslist you can hire someone by days end- yes I have. Of course this eliminates service companies that require high skill level or certifications but there are still more then 50 you can choose from.
I encourage you to go to our store at www.newbizcoach.org and get our ebook- How to be a Part-Time Entrepreneur with workbook for step by steps directions to getting a business up and running in 30 days.