You are getting a little bit of weird advice here, though the LRAP explanations are on target. Getting a PhD after a JD is a common way to get into academia, much more common than the reverse. This makes sense because, if your interests aren't focused and developed enough to get you into a PhD program right now, law school is a great place to work on that. I recommend this aggregation (and previous years) to see trajectories into academia right now, obviously google the people for more info also:
http://prawfsblawg.blogs.com/prawfsblaw ... -2014.html.
If you do feel ready for the PhD, it's worth considering joint degrees, since these can save you time and money and have other advantages for your research timing. Yale, Harvard, and Stanford will all give full or partial (Stanford does 2/3 usually, last I checked) scholarships to JD-PhDs when they obviously don't do that for anyone else. Schools that do have some standard full scholarships also will often reserve one for you as a JD-PhD as a favor to your department, as long as you're not too far off the normal qualifications for these.
If not doing a joint degree right now, these are the financial possibilities I know of:
1) Little or no debt
2) LRAP that covers PhD years and other low-earning academic years, as explained by the poster above me
3) Loans are deferred and do not accumulate interest
4) Loans are deferred and accumulate interest during some or all of the 6+ years you're earning the PhD
5) PLSF?
For #2, as far as I know, only Yale and Harvard are in this category. Notably, Stanford's LRAP is very academia-unfriendly.
For #1, a number of schools explicitly or in practice favor academia-oriented and interdisciplinary people for the big scholarships--off the top of my head, NYU Furman, Penn Levy, various others.
For #3-4, you need to have a long chat with the financial aid office of every school you're seriously considering. Small policy variations will make a big difference for you.
#5: Honestly, I have not looked into this and can't say much about whether and how it can help you here.
Some of this stuff it just won't be possible to figure out for sure until you're admitted and you see what they're offering. This is an uncommon enough path that the policies may not be set in stone, are unlikely to be clearly laid out on the website, and may not even be well-known to the first person you talk with. Apply broadly and be prepared to do a bunch of research in the winter and spring.
I do want to make a pitch for putting yourself in #2 or especially #1 if at all possible. To have the best shot at academia, you need to be able and willing to move multiple times to fairly arbitrary locations and operate through many years of lower income. Big debt is a real obstacle in this and may reduce your likelihood of ultimately ending up in academia more than would the slightly diminished placement power of a lower-ranked school, as long as you're staying in the group of schools that regularly produce academics. And also as long as you're choosing a school where there are faculty in your area who are likely open to working with you--if you're comfortable talking about your potential research at this point, you should definitely get in touch with faculty in both the law school and in your department of interest once you're admitted and deciding.
Anyway, good luck, OP, and feel free to PM me if you want to chat more about JDs and PhDs.