All the visitors except Indians need a visa to enter Nepal. Visas are issued for 15, 30, and 60 days. A single entry visa costs US$ 30 for 60 days and a multiple entry visa valid for 60 days costs US$80. You should pay in US dollars and have with you one copy of your passport photo.
One month visa extensions are available form the department of immigration in Kathmandu. They cost $us30 per month. As a tourist you can only stay in Nepal for a maxim five month period in any one year. It is possible to get a visa for longer than five months by studying, teaching or undertaking research at the university or any institution recognized by the government.
A visa can be obtained at the airport on arrival or at any border point with India, or you can get before you depart form the Nepalese embassy in your country. You can ask for further information at Kathmandu Immigration office.