Many areas of Nepal is either comes under restricted region or conservational region. Remote rural areas, particularly close to the Tibet border, require a restricted area permit from the government of Nepal. This applies to those trekking in the Manaslu, Mustang, Nar-Phu, Tsum Valley, Dolpo, Humla, and Kanchenjunga regions.
Permits range from US$10 to US$500 per week and you will need the help of a registered trekking agency to secure one. Similarly, you have to get permits to enter in another region as well. Plus, to enter in monuments you have to take tickets that come in a few bucks.