Check out your county's website and find out the requirements for operating a retail business. Generally, you will need a business license and State resale license.
Obtain a business license from the county that you will be selling in. Don't forget to go to zoning and make sure your location is approved as well.
Once you have a business license, you may contact your State's Department of Revenue or Tax Collector and obtain a resale certificate. This is usually free.
If you have a particular author or type of book you would like to sell, contact the publisher directly. If you buy a large enough quantity, they may sell to you directly at wholesale rates.
Explore the web. Depending on what kind of books you are looking for, there are several places where you can begin. DollarDays has books, calendars, journals and other items for wholesale prices. Ebay also has a page that specializes in lots of wholesale books. See resources for some vendors. Make a list of your potential vendors.
Contact the vendors individually. Work out arrangements that work best for your situation.