Q: Which mission agencies can someone 18-21 years of age with a high school degree join and begin active service as a missionary?
A: There are many. Here’s a few.
Look at interdenominational agencies including:
Operation Mobilization
http://www.om.org
Youth With A Mission
http://www.ywam.org
International Teams
http://www.iteams.org
A number of denominations have opportunities including:
Four Square
http://www.foursquare.org > World Base