Pros and cons of teaching assistantship as a masters student intending to go on to industry job
I can't really comment on the financial side, that all depends on your own financial situation. The main advantage of TAing, besides the money, is that if you want to teach in the future in any capacity then getting some experience teaching is vital. If you don't plan to teach in the future, then the work experience is probably negligible. There are probably some "soft" benefits that could be useful in industry, such as learning to effectively condense and explain material in your field, but I doubt they would be very helpful in terms of getting hired.

In terms of balancing work, that also mostly depends on the courses and your own productivity. I will say that at many PhD programs, 3 courses + a 15-20 hour TAship is a pretty standard workload for the first couple years (assuming you don't do significant research your first year or so), so it's probably doable.