Why not try Nairobi/Kampala first? Or even Joburg or Durban? There's size able software industries in these places and you could probably even attend the interviews in person.
Blah blah, globalized economy, blah blah. But I would love to hear other Africans from Kenya, SA, and elsewhere chime in and correct my foreigner BS here. My time there was short, so I can be way off base.
As for costs of living, 50k is a really good salary. See the "developer big mac index" here: SA ranks number 2 https://stackoverflow.com/research/developer-survey-2015)
Milage varies if you have dependents to support though - private school especially gets expensive if you choose go that route for kids.