Based on the tags you attached to your question you're looking at a corporate career and I would argue getting your masters would be a good idea for the following reasons:
- You're correct - it's much hard to go back to school later, not so much because you want more money, but because you end up with more financial and time obligations (work, marriage, children ...). It's easier to complete your education before you encumber yourself with those additional responsibilities.
- A 4 year degree is more or less a check box for most corporations today so it doesn't differentiate you candidacy for a job much. Therefore, a masters and doctorate are necessary for your resume to stand out in the crowd.
- A masters program does provide more depth and training related to a specific market. That depth and skill building can be very beneficial. Obviously, an MBA isn't just a good idea if you want to go into finance, you need the additional training and skills the MBA program provides to enter the financial services vertical. That can be true for other careers and as Charles indicates, a Masters or PHD is required to teach at the college level.
- Education is a privilege and it makes sense to take full advantage of it if it's not going to burden you with a lot of loans. Loans are not a good way to start out your adult life so I would balance your academic ambitions against a loan free exit from college.
In short, get as much education as you can afford while you're young and unencumbered. You won't regret that you did.