Hello,
As Idriss said, it would help if u could obtain an Ethiopian citiznship. Foreigners need at least a capital minimum of $ 100,000 to start business in Ethiopia, if in partnership with Ethiopian,the requirement is $ 60,000. Investors in technology and consultancy are required $ 50,000 which will be lowered to $ 25,000 if in partnership with Ethiopian.
If you are an investor or have a business to run in Ethiopia, work and residence permits are not problems. Visa can be obtained at the airport of entry or at the Ethiopian Embassy in UK which will be easily renewed while you are in Ethiopia.
Obtaining investment/business license in the business area you plan to engage is a requirement which does not take more than one week if you fulfil the requirements.