With tourism a very vital part of the city, you can naturally expect that Istanbul has accommodations ranging from the most luxurious palaces (that are also hotels), inns that bear the nostalgia of the past, villas and apartments as well as hostels and pensions for the budget conscious.  For hotels in Istanbul, the accommodations include breakfast for the next day (expect for some hostels and no-star hotels).

The accommodations in Istanbul are classified as:
akgun hotel 5 star
    5-star hotels.  Expect all the bells and whistles of hotel services.  These are usually international chains (including the Sheraton, the Regency Suites, Hilton and so on), however, there are also national chains (such as the Marmara, Merit and Dedeman).  Of course, you will have to pay premium rates for these hotels.  Other 5-star hotels have been homes of the Ottoman Sultans, like the Ciragan Palace.
best western senator hotel 4 star
    4-star hotels. These hotels offer service that’s a notch lower than 5-star hotels.  These are usually equipped with a good pool, a decent bar and restaurant, as well as air conditioning and a staff that can speak multiple languages.

    3-star hotels. Medium comfort level, rooms are equipped with air conditioning, TV and a minibar.  Roman showers, rather than tubs and baths.
silviya hotel 3 star
    2-star hotels.  Somewhat comfortable, may or may not have a television in the room.  Roman showers for the bath.

    1-star hotels.  For those who are on the budget, these offer basic accommodation and a decent private bath.  Roman showers for the bath.
amber boutique hotel
    Special-class hotels/Boutique Hotels/Inns.  These are places with their own unique niche.  You have a choice between period houses, mansions, homey inns and spanking brand new resort-hotels.  Daily rates really depend on the kind of accommodations these offer.

    Hotels with no star.  Simple and cheap.  Don’t expect much, all you’ll find is a simple bed.  Bathrooms are communal.
istanbul apartments
    Villas, Apartments and Flats.  For those who long for a home away from home.  This is for those who stay for more than a week.  It gives you the privacy similar to what enjoy in your own home.  You can do your cooking, invite friends over and basically just about what you can do back at your place.

    Hostels. For backpackers, hitch hikers, the young and not-so-young, hostels provide a more enjoyable alternative than the no-star hotels.  These usually have shared bed-rooms and baths, but generally have a warm and friendly atmosphere.

The districts where most of the hotels are to be found are:
ciragan palace
–    Taksim (At the European side, this is where you will find budget-friendly hotels, and even a couple hostels)
–    Sultanahmet (Usually specialty hotels – old houses and mansions converted into hotels.  Some of these hotels have terraces that offer an excellent view of the Golden Horn.)  You should not, however, that accommodation here is more expensive.
–    Harbiye (also at the European side, these are where you can find the new hotels.)