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Depends on what you mean by “earn a living”! At most schools, putting in the maximum hours possible as a TA will still not bring you above the poverty line - it is better in engineering and sciences than in the humanities, but it is still not much money to live on. Some schools cap RA salaries to similiarly drab levels, others allow the advisor to set the remuneration individually (within limits). In both cases there may be graduated salaries depending on your experience and qualifications.</p>
<p>As a warning, be very clear on the nature and rules regarding tuition waivers - while engineering and science departments are usually pretty good, some still have “assistantships” that are really just hourly work with no tuition waivers. Others may waive tuition only to a certain point - perhaps just the in-state portion, still leaving you with thousands in tuition each semester. This is not tremendously common, but you should still watch for it.</p>
<p>As another warning, make sure you understand how funding is awarded and when/how it is announced BEFORE taking an offer! Some departments will award assistantships up front, others will leave you in some sort of limbo from which you may never emerge, and others will simply expect you to pay your own way the first year or two, or may cap you at Y years of assistantship before making way for someone else. Just be clear - I received admission to UT Austin in ECE, and while I WAS told that I had my choice of 1 TA or 2 RA positions, I was ALSO told that the actual pay for those positions would not be set until August - four months after they expected me to accept!! Not knowing whether I would get $13k or $34k per year meant I went somewhere else.</p>
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b@r!um covered the TA part pretty well - basically anything that needs to be done, you might be asked to do it. If the professor knows you are interested in an academic career (or is busy or lazy) you might see nearly every aspect of teaching a course, including writing exams or co-authoring course notes. If/when you demonstrate advanced skills, you may simply be the instructor for the course - as long as you have a masters degree you can teach, and some advanced PhD students do just that!</p>
<p>As for being an RA, I should note that most professors will expect your actual RA hours to represent work above and beyond what you need for your thesis. Hopefully it inspires your thesis, supports your thesis, and improve your publications and credentials for when you graduate, but expect to spend these hours helping him/her to write grants, write/edit papers, edit textbooks, work on their projects, supervise “lesser” lab students, assist other grad students with THEIR theses, etc. An RA where you have no responsibilities other than your own thesis is really just a misnamed fellowship.</p>
<p>That having been said, please note that there are other options as well. Some schools have “graduate assistantships” or “GA’s” where you get paid and get a tuition waiver but assist in more administrative roles - don’t ask me for details, I have seen them listed but don’t know anyone who has had one. Also, the apex of the funding ladder is a fellowship, which may be awarded by the department, the college, the university, or an external agency, and which (as I noted above) gives you the money and the tuition waiver without generally requiring that you do any (or at least much) work for it - these are usually much more prestigious and pay pretty well (my fellowship offer was $35k/year for 5 years guaranteed), but are often awarded based solely/mostly on GPA and GRE scores (or other widely-comparable things). Plus, the most famous and common fellowships are awarded by the US government and are generally available only to US citizens.</p>