I've seen a lot of posts here and elsewhere about how difficult it is to get a research career. These are quite discouraging to me. Is it really so impossible? I am a master's student now (in linguistics). What I would like to do is to get a PhD in linguistics, doing fieldwork on an underdocumented language and then move to a country like Mexico permanently to dedicate my career to studying the indigenous languages of the country. Is this possible? How difficult would it be to get a job? How should I go about pursuing this goal?
The most important things are: Find a Ph.D. advisor who has good projects and a good network. And simply do some good work yourself. Apart from that, never forget that pursuing a career in academia just means taking part in a lottery. Don't take it too seriously if you don't succeed in terms of jobs.
There are a few possibilities for such a career. One is Bible translation if you are so inclined – that is the dominant form of such language-descriptive employment. You would have to contact someone in that business for details, but as I understand it, you get sent somewhere, and it just depends on where (if) they have a need / interest. You don't even need an MA to do that (though you will need to go to summer training camp). Another option is an academic position in linguistics in a foreign university such as somewhere in Pakistan, but again there is the question of need and also official policy (in some countries, there is little support for research into indigenous languages, perhaps even strong opposition). Then finally, there may be some local indigenous interest group looking for a linguist. For Mexico, you might want to consult the INALI website, but there doesn’t seem to be any indication of a “help wanted” section there.
It’s not exactly clear what you want to do (and why), and what skills you have to offer. A combination of computer skills, language-analysis skills, and actual knowledge of a reasonably large but not really large language could result in employment in situ at least for some years (for example working on a spell checker in some poorly-documented and un-supported language). Mexico might not be the best bet because they have quite a number of well-trained linguists working on projects, whereas certain places like Eritrea don’t have a local linguistics community. The current trend is not to seek outsiders to work on the local language, rather local speakers of the language are trained how to do the necessary research.
One approach taken by some is to do linguistic work on local languages as a hobby, and get a more permanent job teaching English to support yourself.