I didn't know that about doctors. I do know that if you are interested in teaching foreign languages at any level and you have native language skills, you are good to go. I know there is an overabundance of lawyers, business majors, etc.

As far as salary, the jobs with the best salaries in my field usually look for experience. For example, you can get a job that pays dirt in Harmon Hall, they will fully train you to teach English, then work for a little bit then piggy back off of that to a really good job at a corporation or car company. I'm getting 160 pesos an hour now, but I wouldn't have got it if I didn't do student teaching in the US. But my other job at the small university I also work in didn't really care so much about the experience, they were just looking for a native speaker.

The cheaper properties I have seen have been as low as 2000-2500 pesos a month for a 1 bedroom small place with no garage, one bathroom etc...there are lower ones but they are literally run down shack looking places I wouldn't want to live in.
As far as buying, it varies a lot but it is still much cheaper than the US. You can get a really big, really sweet place that has room for kids, a lawn, and everything if you can pull in 20000 pesos a month. That's about what you would need in salary to get the loan for the really nice, really big places.