WSO is a great place to see other people's questions on this stuff so you might want to check that out.
Starting pay at an okay shop should land you at least $150k but good shops will be north of $200k (Citadel, DE Shaw, Two Sigma, etc.) Quant salaries vary greatly, however the upside is practically unlimited. Not sure about other firms but at Citadel they generally don't go above 60/week.
Spend some time looking at the applications for places/roles you're interested in as they will be rather specific on qualifications and background.
I'm assuming you are looking to be a Quant Researcher which is where the real work is done. Many places will look at your thesis and go hardcore on poking holes in it so be ready to defend it. Your ability to research and possibly implement solutions is what they're looking for here.
HFT quant work generally utilizes C++ for execution of a strategy as it runs fastest. Python and R is useful for research and analysis. In this area I'd recommend reading This Book written by a former AQR quant.

Also I've heard good things about this book This Book. But haven't gone through it myself.
Jobs are pretty stable as long as you are good at what you do. Good quant divisions will have phenomenal returns and the employees will have a good work/life balance.
Location-wise NYC is naturally the best place, however Chicago would be your #2 bet.

Python is an excellent tool for analyzing large data sets. There is many modules made to Python that makes implementation of rather sophisticated systems such as ML easy.

A good place to start: http://www.amazon.com/Python-Finance-Analyze-Financial-Data/dp/1491945281

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