The best license is the license that allows you to purchase vehicles from wholesale (dealer only) auctions and sell to the public such as to your family and friends. 

To get an Alabama Dealer License you will need to do the following: apply for a tax number, complete an Alabama Dealer License Application, purchase a surety bond, secure insurance, pass local zoning and complete, and provide other documentation and fees.
 

Is there an Auto Broker license or endorsement?  Yes. 

To become eligible to obtain a BROKER license in Alabama, an applicant who does not hold a license in another state must:

Be a U.S. citizen, permanent resident alien or legally present in the U.S;
Be at least 19 years old;
Show proof of bona fide residency in any state in the U.S.;
Show proof of high school graduation or the equivalent;
Not have been convicted of a felony or a crime involving moral turpitude;
Not have had a application or license rejected or revoked in any state within the past two years.
After meeting the education and/or experience requirements, pass the licensing examination.
Additionally, a BROKER applicant must:

Successfully complete an approved 60 clock hour prelicense course.
AND
Must have held an active real estate salesperson license in any state for at least 24 months of the 36 month period immediately preceding the date of application.

Any other license required like salesman license? License is required of any person or entity who is engaged in advertising, selling, buying, or negotiating for sale five or more motor vehicles in one calendar year.

Office Space Requirement: Before you can be issued a car dealer license, you need to have a permanent business name and business location. As part of the dealer license requirements, you’ll need a permanent sign affixed to the property if you plan to be a retail dealership.
Display Space Requirement: This business location must have a display area, an office, and a phone system with a publicly listed number.you’ll need a permanent sign affixed to the property if you plan to be a retail dealership.
Required Office Hours: Complete an Alabama Car Dealer License Application https://www.revenue.alabama.gov/motor-vehicle/dealer-license-and-dealer-license-plate-requirements/
Pre-site Inspection or Zoning Certificate? Must meet all the local zoning requirements.

For help finding a startup location, go to www.dealerspace123.com

The first step is to take the Dealer Pre-License Training Class. 

Link to preferred Pre-licensing educators: https://www.alabamaiada.org/pre-licensing/

Mail the $150.00 filing fee and two original copies of the "Foreign Limited Liability Company Application for Registration" to Alabama Secretary of State, Attention: Business Entities Division, P.O. Box 5616, Montgomery, Alabama 36103 or 770 Washington Ave., Suite 580, Montgomery, AL 36104.

To apply for your Employer Identification Number (EIN), visit the IRS website. It's FREE to apply.

You may need these numbers: NAICS Code for Used Car Dealers 441120 and SIC Code 5521.

For help incorporating your business to sell cars, go to www.autodealerbschool.com/recs

To apply for a retail used car license, you are required to have a surety bond and garage liability insurance.

Here is a list of preferred providers www.autodealerbschool.com/recs

To apply for the retail license, you must complete all the requirements and submit a paper application.

For help submitting your application, join Drama Free Licensing VIP.
Click here for details: www.autodealerbschool.com/DFL

The board rules will have all the laws that govern auto dealers, you can find them at: https://law.onecle.com/alabama/title-8/chapter-20/index.html