Bismillaah Al-Hamdulillaah wa salatu wa salaamu 'ala rasulullaah
The Ways of Acquiring Sustenance: http://www.salafiebooks.com/se/dld.cfm?a=tuwjjz
11. Migration in the Path of Allaah
The evidence is the Saying of Allaah, The Exalted:
He who emigrates (from his home) in the Cause of Allaah, will find on earth many dwelling places and plenty to live by... (An-Nisa`, ayah 100)
The one who emigrates in Allaah's cause will find goodness and blessing and also plentifulness in the means of living.