Being a big city Tehran offers a lot of places to stay in if you are on a budget.
This hotel has the best receptionist Mr. Mousavi who is there to help you with anything that you want. It is a small hotel, with small rooms which have a TV, fridge and private bathrooms with shower and basin, whereas the toilets are shared.
This hotel is located near the Treasury of National Jewels and the Turkey Consulate. The managements speaks well English and very helpful. The rooms are small and clean, with fridges, fans and bathrooms. The hotel also has a restaurant which is open for lunch and dinner.
This hotel is very old and it is listed as a historical monument in Tehran. It is decorated in and old style. The prices of the rooms are very cheap, might even be the cheapest. Downstairs there is the Cafe Naderi where intellectuals and writers meet. The from rooms are pretty loud because of the cafe, so make sure that you ask for a rear room.