I'd like to chime in here because I'm a registered patent agent. You do not need a PhD to become a patent agent, only a techincal background (BS or related undergraduate course work in science or engineering) in order to sit for the patent bar. Upon passing the patent bar, you are a registered patent agent and can work in patent prosecution (i.e. draft patent applications and argue for the patentability of your client's invention). You cannot, however, litigate. Only attorneys can litigate, whether they are patent attorneys or just regular attorneys.
Patent agents typically earn fairly well (about $75K per year) with the appropriate background and experience. I mention background because, unfortunately, one who holds only a BS degree in a life science (e.g. biology, chemistry, etc) cannot usually expect to make that kind of coin. So if you're looking forward to some decent coinage, and you only have a BS is biology or chem, you should seriously consider obtaining an advanced degree (PhD or JD), or just go back and get a degree in electrical engineering!
Kinda makes you wish you took the easy Business classes in like all your rich friends. The road is long for the science major.