Renting out your property in Spain comes with the same pros and cons you might find anywhere: you have the opportunity to pay for and even make money on your investment, but you run the risk of running into less than respectful renters.
There is good news, however, in that Spanish law has evolved favourably in recent years, both for landlords and tenants. Read more about this under the section titled "Advice for Tenants"
Of special interest to landlords is the possibility of asking long term tenants to pay their the community fees and municipal taxes associated with the property. But, be careful. This arrangement must be clearly stated in the contract and you should have proof that the tenant clearly understands the deal, otherwise they can take you to court - and win the right not to pay these fees.
Also of interest to landlords is the right to ask for a deposit - something you should definitely do. You are allowed to ask for one month's rent down for an unfurnished premise and two months' for furnished and commercial quarters. Obviously, as landlord, it would be most convenient for you to collect this deposit yourself for safekeeping until the contract ends, however, the right thing to do is to put the money in the hands of a neutral third party - either an agency or a government office called the "Consejería de la Vivienda". To find the branch nearest you, ring the Málaga office on 951 038 355. These third parties are responsible for returning your deposit only when both parties are in agreement.
You can handle the rental of your flat, villa or other property yourself, or you can put it into the hands of a property management company. Often there will be a management company located in your urbanisation. However, do check credentials carefully as all manner of problems can arise when dealing with a less than reputable company. For instance, there have been cases of rental managers letting property while owners are out of the country, and then keeping the money for themselves. An inexperienced manager might also be less than adept at sorting the wheat from the chaff when it comes to accepting clients.
Finally, by law you are supposed to declare rental income, but many properties are let on the black market with only verbal agreements between landlord tenant. Be advised that should you choose this route, a contract still exists between you and your tenant in the eyes of the law, and should any disagreement arise, your tenant need only prove payment of the last month's rent in order to initiate a complaint against you.