You raise a good point Chris, but your mistake is in assuming that I intend to go back in forth a lot, and that intend to live a "comfortable life."
You must also keep in the mind that the money I do earn while living there... which by the way is where I intend to live forever if I choose this path, will go into the local economy. I would be an immigrant.
The "taking jobs" theory is relevant still, though, to be sure.
However it is my understanding that there is simply not enough manpower. Not enough "qualified locals," as you say. There can be, but they must first become "qualified." I would argue that this is where I come in.
For instance, imagine if every child in Togo had a school to go to. That in itself would be a miracle, but each of those schools needs teachers. As it stands there are not enough qualified locals to do those jobs. Expand this to other areas besides education, and you will begin to realize that I am not taking anyone's job. Every local who can work in those fields already is, or else they are overseas.... just like me. So look at it this way: my moving to Africa is essentially canceling out on African from the same place with similar skills who decides to move to America for a better life.
Obviously I do not dispute that this is also selfish for me, I do not intend to sound like some selfless martyr. I will be the first to contend that every single action any human ever undertakes is inherently selfish. However in this case my selfishness is not in that I am only there to gain experience, knowledge, and perspective for myself, because this implies I will be there temporarily. Though it is true I will gain those things, I will apply them in Africa, not elsewhere. I intend to remain there once I arrive, you see. So it's not as though I intend to use this experience as a bullet point on my resume for an UN office job. That's why I'm hesitant to agree that I can "just switch from one path to the other whenever." Perhaps so, but I do not know if I am willing to do so.