I went to grad school in math straight from undergrad. Looking back, I definitely think that students considering grad school should make sure they have some financial stability before going to grad school. I would advise my former self to work for a few years at a "real job", save up some money, start a retirement account, etc. Then, once you have that, you can go to grad school without worrying too much about not having much of a salary, because you have money saved up and you're not living paycheck to paycheck, so to speak. And your retirement account money will be accruing interest while you're in grad school.
As pointed out in the comments, salary varies quite a bit depending on the university. Private universities probably pay a lot more. I went to a public university. We went on strike for better pay. It would be nice if we didn't have to do that.
One benefit to being a grad student, though, is that as long as you maintain good academic standing, you should be fully funded for several years (around 5 or 6). This means you basically have a guaranteed source of income and you don't really have to worry about being fired. This is in contrast with many "at-will" employers, where you can be fired at any time and, oh well, you're out of work.
Also, if your advisor can fund you with a Research Assistantship, it basically means that you can get paid to do math and not have to teach. You can wake up whenever you want, sleep whenever you want, work some days and not others, etc. You basically have complete freedom, and you get paid!
In addition, funding could be tight during the summer months, with fewer students enrolling in courses. When I was in grad school, summer funding was typically given but not guaranteed. If you can get a summer internship in industry, you could be paid a lot more than you would by teaching summer courses. And you would pick up valuable industry skills. So consider setting aside some time to look into that.
In general, what counts as "enough" varies from person to person. Some people need more money to support their lifestyle and their personal needs than others. However, one thing some mathematicians do is the following. They apply for a position at a different university and get it. Then they tell the department chair, "I got a position at this university, and they will pay me X amount, which is more than I'm making here. You'd better increase my salary, or I'm out of here!" The department says, "OK, we'll pay you more. Please don't leave!" And they say, "Thank you. I'll stay."