JohnnyP
Oh yes, AirServ guys are definitely paid!
If I remember right for instance, AirServ Entebbe (Uganda) operates C210, C208 & BE100. A Caravan captain (single-pilot) there was paid 2500 USD/month with accomodation & food provided during the mission and 5-months-on / 1-month-off schedule.
As far as their requirements are concerned, they were not very high but they wanted you to come with a type rating and a South African validation. Many AirServ aircraft in Africa are operated under ZS- registration (South Africa), I believe it is a subsidiary of the main AirServ.
Finally, I am not convinced they are really Christians... Definitely strongly affiliated to the US government, but not really big on the religious side unlike some of the missionaries who operate 206s and the like...