Suitable option can choose and demanding traveler, not limited financially, and unpretentious economical tourist.
Relatively inexpensive accommodation in Nairobi will provide hotels with 1-2 stars, so-called bed and breakfast hotels. Here you will be offered a private double room with bathroom from 54-68 USD (as options - Khweza Bed & Breakfast and La Jardine).
So, how much does it cost to stay in Nairobi in hostels? For example, in Nairobi Airport Stop Over House, which is located near the international capital airport, for a bed and breakfast you need to pay 24 USD. To stay in a guest house in the Karen neighborhood, near the National Park, you will have to pay from 33 USD per night (Hope Guest House).