The fact of having a girl friend does not make any change, unless you marrie, but even this will take you 2 years before you can recieve legal status based on a marriage.
A small business is not really supported by the government, foreign investors need 200K USD capital, in a joint venture it can be reduced to 150K...having a Ethiopian partner. For sure if you find some one, local who puts the ammount on the table you can start, but always with a risk. How much you are holding of the 150K is not the question!
It is not easy due that Entrepreneurship is not really wanted.
Oliver