If you will send me your e-mail address, I'll e-mail you (in Adobe Acrobat pdf) the text from a chapter of my new book, Adapter Kit: Belize (to be published in August by Avalon) on living/retiring and investing in Belize. The chapter will explain the rules for working in Belize.
In general, as was stated, it is not easy to get an official work permit. Salaries are low, and good jobs are few (and the goverment naturally saves those jobs for Belizeans, just as the U.S. government tries to save U.S. josb for Americans).
Renting is fairly easy, but it's something best done after you arrive. Keep in mind that Ambergris Caye has artificially high costs for most things -- it is an island, it is the main tourist center, and it is popular with expats. Other areas of Belize are much cheaper. Nice rental houses in places such as Corozal Town are available at a fraction of the cost of those in San Pedro.
Belize First Magazine http://www.belizefirst.com/