Rental contracts are usually written in Spanish and only some landlords will translate them into English. Even if they do translate them, you should always consult a professional translator as any misunderstandings will be at your expense.
What expats love about Nicaragua is that a lot of things are negotiable, even rent. Longer leases are particularly open to haggling, with one outcome often being that the rent will go down the longer you stay in the property.
Legally, rental contracts in Nicaragua can only last up to four years. Other than that, the length of time is negotiable between landlord and tenant. Two months notice before you want to leave the house is the standard.
The payment of a deposit is not required by law, however landlords usually request a payment of one month's rent in advance as a security deposit. This deposit should be described in your contract, so make sure it is to minimise any future problems.
There is a legislation that regulates the relationship between landlords and tenants, which is called the Código Civil de la República de Nicaragua. It is very pro-landlord and tenants rarely win in the event of a disagreement, so try to sort out any misunderstandings directly with the landlord and an interpreter if necessary.