There is an exellent article on Queen's Law Life looking at law tuition compared to law professor salaries. It is insightful commentary on the current state of law tuition. I found it very illuminating.
You may want to do some futher research into law school tuition at your school of choice. Is it comensurate with what you hope to get out of law school? Will it allow you to make the kind of money that you want to make?
One other comment that I would like to add to the matter is that law professors often begin their professorships with an LLM (Master of Laws). They do not require a PhD, although some do achieve this degree. It's true that you require two degrees before becoming an LLM candidate, and that many people consider the LL.B/JD equal to graduate school (i.e. a Masters level), but it is still worth considering that law professors do not require that PhD status. In fact, I had some professors who had been teaching for many years with only an LL.B. degree.
You can also find further discussion here and here (very interesting to me) on the LL.B / JD (Bachelor of Laws vs. Juris Doctorate of Laws) on Queen's Law Life.