I am assuming you are in the United States. If not, the situation in your country may be a bit different.
If you decide to be a faculty member for a school of nursing and need supplemental income, your best bet is probably to work part time as a staff nurse. Picking up an ocassional shift can be quite lucrative, particularly if you do it on nights, or on a weekend, or holiday, etc. Those shifts often work best for faculty, anyway -- and they will help you keep your clinical skills current. At my hosptial, we waive the minimal shift requirement for faculty members who teach clinicals here to try to make it easier for them to work an ocassional shift because everyone benefits from it. The faculty members stay current, we feel safer about trusting them with our patients when they are here with students, etc.
On the downside, if you spend too much of your "off time" from school working as a staff nurse, you probably won't have time and energy to spare doing some of the things your school may want you to do to advance up the career ladder there (such as research, publication, committee work, etc.). So be careful not to jeopardize your faculty job by doing only what is minimally required there. If your faculty job is going to be your primary role, you'll need to devote most of your time and attention to being successful there.
As for education roles within a hospital ... different hospitals sometimes use different terms to describe the same thing. The specialty of "professional development" as an organized specialty group is fairly new. In fact, just last year they changed their name to the "Association of Nursing Professional Development." In 2008, they devloped a new model and set new standards defining the scope of NPD practice, etc. Not every hospital around the country has used that model and those standards in their job titles and job descriptions. You will find lots of variation in the field.
But in general, NPD Specialists are graduate prepared nurses who specialize in Nursing Professional Development. They tend to make more money than new MSN level faculty members because they are paid on a hospital-based pay scale. They can work either in a hospital's centralized education department -- or report to the director of a particular unit. Usually, the full focus of their job is education -- and perhaps some project management, policy development, etc. thrown in. The term "clinical educators" can mean the same thing, but it can also refer to someone who is a little closer to the staff nurses in terms of role description. Some educators are expected to work as a staff nurse sometimes and do direct patient care -- and/or their focus is on education for one unit only -- while the centralized education department does larger, hospital-wide programs. You would have to look at a particular facility's job descriptions and organizational plan to identify the particular job titles and responsbilties of the educators at that facility.