Baja is a peninsula with the Pacific Ocean on its western shores and the Sea of Cortez on its eastern shores. Its northern border is California. There are 2 states in Baja: Baja California (Norte) and Baja California Sur. The main entry point is the city of Tijuana, right across the border from the San Diego area, and this is the busiest border crossing in the world.
In
Baja (Norte), the main cities/towns run from Tijuana to
Ensenada on the Pacific side, and Mexicali to San Felipe on the Sea of Cortez side. The Ensenada corridor, which includes
Rosarito Beach, is the most popular for Americans because it is very close to the USA. These are "drive to" places; no airports to speak of (except in Tijuana).
In
Baja Sur the main cities/towns are the famous
Los Cabos at the very end of the peninsula;
La Paz, about an hour's drive north of Los Cabos; and
Loreto, a fast growing community north of La Paz. You have to fly to those cities (you CAN drive, but you don't want to if you aren't familiar with Baja).
You will need a tourist visa, called an FMT, if you go south of Ensenada or stay longer than 72 hours. You get your FMT at the border crossing (it only takes a few minutes), and it costs around $20 or so; it is good for 180 days. You will need to show personal identification; it's a good idea to have a passport.
A work permit can be more difficult. Generally, foreigners cannot work at a job that a Mexican can do, so you won't find foreigners doing many "regular" jobs. That is why so many foreigners sell real estate and timeshare in Mexico, or open their own businesses. A work permit is a type of visa called a Nonimmigrant Business Visa (FM3) for multiple entries. Here is where you can find out about the different kinds of visas:
http://www.mexperience.com/liveandwo...ing_mexico.htm
The best place for lots of information and asking questions is on the
Baja Nomad forums.
I hope this is helpful to you, and if you decide to visit Baja I hope you have a great time!