I was reading The Martha Rules by Martha Stewart the other day (she was inspired to write it when a fellow inmate asked her advice about starting a hair salon combined with a restaurant). She has a friend who started his own exotic plant nursery. He often counsels people who want to begin their own nurseries that their biggest investment in the early years will be a wheelbarrow and a shovel (unwelcome news to those who see starting a business as an opportunity to go on a spending spree).
The library has an extensive collection of books on starting businesses. I've listed some titles on starting a home based businesses, for those who want to start small:
101 Best Home Businesses
101 Best Home-Based Businesses for Women
The Best Home Businesses for People 50+
McGraw Hill's Careers for Homebodies and Other Independent Souls
Entrepeneur Magazine: Starting a Home-Based Business
Entrepreneur Magazine's Ultimate Book of Homebased Franchises
and then there are some very specific ones, such as:
How to Start a Home-Based Craft Business
How to Start a Home-Based Catering Business
How to start a Home-Based Professional Organizing Business
You can check out your potential competition (at least, those who advertise in the yellow pages) by searching ReferenceUSA, an online database the library subscribes to, by clicking here. Guided Search will let you choose a type of business via yellow pages heading and you can choose to search by a lot of geographic factors (my favorite is radius, which lets you choose how many miles to search around a particular zip code).