Rental contracts in Iran vary quite dramatically, so it is important to have a agent to do this and also the agent should help you to fully understand the terms of the lease they are signing. Most rental contracts will be set for a period of one year, although in some cases, expats will likely be able to negotiate shorter leases if necessary.
Renters are usually required to pay a sizeable security deposit to secure the property and compensate for any damage. The deposit is returned at the end of the lease, provided that the property is left in a suitable condition.
you can see average price of accommodation in Tehran, here: