1. Yes, sort of. I'm an evening student, to maximize ROI on the degree. On one hand, it sucks having a 16 hr day 4x a week (full time job M-F, school M-Th til about 9:30pm), but on the other, it's preparing me for the hours I'll put in once I graduate. The coursework is great, but the overall schedule is draining.
2. None. I have a business degree and a full time job within an unrelated career track (although a JD goes pretty far in my company, even in non-legal paths, which gives me more options at graduation).
3. Yes, I took a year off to make sure it's what I really wanted. During that year I had an awful job that I've since left for a better opportunity, and along the way I decided the ROI on the degree made a lot more sense if I had a full time income during school. While I'm still taking on debt for tuition, everything else is paid for, I have retirement savings going at a steady rate, and would be able to pay the loans off on my current salary. Once I'm out, I don't have to take the top dollar 80 hour a week position if I don't want to, and I probably won't.
I'm guessing you're considering law school. Go at night. Evening students get great jobs coming out, despite the stigma attached to it by the day division students. It helps to go to a school with a strong alumni base of evening students and a program that has services accessible to you at night, so make sure you do your research on that. The faculty at my school really likes the evening crowd, so they go out of their way to help, including having clinical courses available, summer/externship placement, etc, and I know many other evening programs around the country have the same things going. If you can handle the demands of work + school, especially if you're working during the day at a place you'd like to build a career longer term, an evening program gives you a lot of options.
Above all, take a year off. School isn't going anywhere. Enjoy making money and living like a 20-something for a little while first. It's worth it. Then, if you really still want to become a lawyer, go.