If you're going to Portugal on a budget, the least expensive accommodation will be a hostel or backpackers. There is a good selection of such places that cater for the more thrifty end of the holiday market and many are extremely well situated.
For backpackers, Portugal's hostels, called pousadas de juventude, provide cheap accommodation. Rooms will most likely be dormitory-style, although there are also some family rooms. The youth hostels linked to the international hostelling network are located in areas with easy access to popular sightseeing spots and various activities.
Bathroom facilities will often be shared, but some hostels will also have rooms with en suite bathrooms. Many have rooms adapted for wheelchair users.
Breakfast is often included in the price, and a number of other services and amenities might be available such as additional meals, self-catering and laundry facilities, and WiFi.
As you would expect, the dormitory-style rooms with shared bathrooms are the cheapest option of all. Prices will be higher at certain times of year, so the budget conscious traveller would be best advised to visit in the low tourist season. .