I'm currently a graduate student who does not work aside from fellowship duties like TA-ing, grading, and such. My approximate income, therefore, is around $18k per year, minus around $2k for school-based fees. I have not deducted rent, food, etc, in an attempt to allow this question to be slightly more general (for the general grad student crowd, at least!) but my situation is around $650 for housing, no car costs, and no outstanding student loans.
Main Question: What are the perks, tax-wise, of investing in a Roth IRA right now? Should one's income verses expenses be above a certain level in order to begin investing in a Roth? Is there an approximate age that one should open a Roth?
(I have checked around the internet, and many of the sources are polarized in "invest early, invest often" and "wait until you have enough, then slow and steady" camps. I am interested in seeing what the contributers to this forum have to offer!)