Getting a teaching or research assistantship for masters degree is not easy. I would suggest finding scholorship/fellowship before you commit to your degree. If you have to worry about how you are going to pay your bills every month, that is not going to reflect well on your classes/research. Unlike in undergrad, you are not going to have 3 months off to catch up with your bills. I do agree that it is morally incorrect to join a Phd program when your intention is to quit after masters degree. But, after joining the program, you may change your mind. 5 years is not a long period of time and you may love your research. From what I have seen, I wouldn't suggest anyone just going for a Masters degree without assistantship before you start the program (if you have a choice). I would go for a PhD.