Thanks for posting this question. I have been wondering about law school, too. It would be a very long shot in my case, since I have a career I like and am just looking for "add-on" legal studies/experience to boost the career I already have. This thread has certainly given me pause!
Currently, I am enrolled in a paralegal certificate program through my local community college. Just to compare the cost - I pay about $250 per class plus maybe $200 for (used) books for each class, and the program requires 8 classes (4 requirements, 4 electives), so the entire certificate will cost me roughly $3,600. In my case, I plan to take more electives, so it might be $4,800 or so, but at that amount, I can pay as I go. Some of the women in my class are career-changers and have gotten scholarships, so it can even be less. I just looked up another university in town that offers a paralegal program, and theirs costs about $10,000 - still a good deal. Online classes are not for me, I need the personal interaction, which has been very rewarding. If you will be looking for a job in the field, don't discount the networking opportunities, either, since after all, the lecturers are lawyers themselves.
I have a master's degree in another field, and I have to say that in no way is this program a walk in the park just because it is a certificate or at a community college, so I wouldn't be concerned about not being challenged just because it's not a JD. While challenging, it is do-able at one class at a time while I am working about 20-30 hrs./wk. plus taking care of a family (2 school-age children) & our activities. I would have to give up an activity (I teach in a kids' program on Saturdays) or make other childcare arrangements to take more classes than that. In general, the research and writing is very interesting. I was surprised to learn what schiljm said above - even if you are used to reading academic material, reading court opinions and similar material takes a *long* time. You definitely need to carve out chunks of quiet time for the reading. I find it easy to work with background noise otherwise, but I find that I can't tolerate very much noise at all while reading legal stuff.
Maybe the lawyers here can comment more authoritatively on the job prospects for paralegals, but I have heard that more work is being handed over to paralegals to do simply because they are cheaper than lawyers, but I don't know that from personal experience.