To enter the country you will need a passport that is valid for 6 months after the date of your return. All visitors need a visa. Ethiopia has an e-Visa program that enables tourists to apply and pay for a visa online. Please be aware there are a number of fake websites offering a visa.
The only real site is; https://www.evisa.gov.et/#/home
For passengers arriving from a selected number of countries it is possible to get a visa on arrival at Addis Ababa Bole International Airport. This costs around US $ 50 and has to be paid for in cash. Visas are also readily available at Ethiopian diplomatic missions abroad.
The currency in Ethiopia is the Ethiopian birr or ETB. It is illegal to enter or leave the country with more than ETB 200 per person in local currency. And cash in excess of US$ 3000 (or foreign equivalent) must be declared to customs officials.