First of all you have to know, that besides the monthly rent you have negotiated, you have to count on some taxes and extra fees (one time payment only). They can increase up to 6 monthly rents (in that case it depends a lot on the negotiation between you and the owner).

Formalities:

It is advisable to go to the Registro de la Propiedad (Land Registry) to check who legally owns the flat.

It is advisable to register the rental contract in the Registro de la Propiedad (Land Registry), which protects you from the sale of the building or the home.

Expenses:

The real estate agency or the owner can ask you for a paga y señal (down payment) as a reservation of the flat, which will then be deducted from the first monthly payment or will be committed to return if the contract is not signed.

If you rent a house through an estate agent, you will have to pay the comisión (commission), which may be that you have to pay half with the owner or 100% as a tenant (which is common practice in Barcelona in today’s transactions).

Provide the fianza (legal deposit) to the real estate agency or the owner, who must deposit with the appropriate regional entity (Incasòl, in the case of Catalonia). This amount is returned when the contract ends, if no clause of the contract has not been breached, nor caused any damage, damage or non-payment. The regional autonomous entity is who returns it to the owner and he transfers it to your account.

In some cases, the owners ask for a depósito adicional (additional deposit) to face possible defaults.

Remember that the rental cost should not exceed 30% of your monthly income.

It is optional but advisable to ensure the contents of your home. Some owners require that you’ll insure your contents within a month of when the contract was signed. The owner must always insure the flat (the building if it applies) and nothing else.

Pay the Impuesto de Transmisiones Patrimoniales (ITP) (transfer tax), which is according to the contract (how many years the contract is written for) and the rental price and varies according to the region (comunidad autónoma).

Supplies:
Don’t forget to change the owner of the electricity, water and gas meters, whether it is purchased or rented.

Movers company:
Don’t forget the costs of a movers company, if the apartment is not furnished or if you move from another home.

Source: habitaclia.com

I hope this article was helpful for you.