In the towns
Accommodation in Nepal is cheap. Nepal's reasonably priced budget hotels, and the lavish and luxurious star hotels will surprise you on just how far your money can go in this country. Some hotels extend special discounts for reservations made through their websites, for reservations made for a group, and for reservations during off tourism season. Be sure to visit their website and look for discounts.
It is also common to ask for discounts, even if you didn't find that information on their website.

The prices for a Hotel in Pokhara or Kathamndu start at about US$5 or even a bit less, depending if shared bathroom is OK or not. Breakfast is normally not included in the budget-hotels, but in the many bakeries in Thamel you will find many kinds of good-priced breakfasts.

Lodge in Thare on the Gokyo Trek.

On the trek
While you are trekking, you normally will stay in Lodges or on camping-treks in Tents. Along the main routes there are many so called "Lodges" where you can  find accomodation and food. With the growth of the trekking industry, facilities have approved and there is now an extensive system of lodges serving major routes. Features such as pavement cafes, sun rooms, private rooms, indoor western-style toilets and electric lights abound. Hotels compete for attention of your stomach with offerings of cake, pie, pizza, steaks, tacos, enchiladas and spaghetti bolognaise.

Prices at most hotels are cheap, but you will probably be quoted the double price or even more if you don't eat in the same lodge which you sleep.
But don't expect too much luxury in the mountains. The "hot shower" may turn out to be simply a bucket of lukewarm water and the toilet may be a latrine behind the hotel. The private room can be a wooden cell with no furniture except a bed with a mattress. People searcheing for "luxury-holidays" are not in the right place here, but the people are frindly and the food is delicious.

In the remote areas you only will find "Bhattis", which are usually wooden or maybe even a bamboo structure close to the trail, with the large house of the owners some distance away. It usually has a simple mud stove with a pot of milk and water to make tea.