If you love economics and are motivated enough to bear the difficulties of a PhD, then go for it; however, you should consider a few points:
1. If you have been off school for too long, you may not be ready for the pressure of PhD courses.
2. By the time you finish your PhD, you will be around 40, at which it is not easy to start a career, I guess. But I'm sure there are counterexamples to this statement.