Rental guarantees are a common feature in today's overseas property market and are used widely by developers to attract investment-minded buyers, looking to earn a rental income from their overseas property. Simply put, these guarantees are a commitment to return a percentage of the purchase cost of a property to the buyer each year for a fixed term. Ostensibly, the developer recoups this money by renting out the property having secured an agreement with a tour operator, or by marketing the property itself, or via a lettings agent.

This sounds an attractive proposition, but rental guarantees should be examined closely. Firstly, unscrupulous companies may simply be inflating the sale price of the property in order to cover the rental return.

"Too often guarantees are just a shallow marketing hook which is being increasingly abused," says Guy Hamilton Simcock of Bulgarian agent Orpheus International. "Try asking how much the property would be without the rental guarantee. This may draw the salesperson into saying we'll give you X off the price - in which case you're being over-charged."

Buyers should also shop around carefully to see the cost of comparable properties in the same area. Find out whether the developer has an agreement in place with a travel company or lettings agent. If not, then how do they plan to find tenants and ultimately pay the guarantee. Examine the fine print of your contract to see who is actually guaranteeing you the money.

'Rental guarantees are marketed with alarming regularity," says Paul Owen, CEO of the Association of International Property Professionals. "The simple rule is: if it is not in the contract, it's not guaranteed. Potential rental incomes are often reclassified by salesmen as 'guaranteed', though this is never in writing. Check the contract and recognise that no mention means no guarantee. Even rental guarantees in the contract should be scrutinised by an expert. Make sure you hire a lawyer to check them before you sign anything."

According to Gurkan Ozcan of Turkish law firm Acacia International, rental guarantee agreements are not compatible with the Turkish legal system and throw up many practical problems. Their legal basis is also far from secure.

"A set annual return on your investment can only be legally guaranteed if the developer provides a letter of guarantee from its bank," Ozcan explains. "However, this would only guarantee you the money for the first year, and would have to be renewed every year by the company."

Ozcan does not recommend entering into rental return agreements, unless you are dealing with a reputable company. However, he suggests that this situation may change in the near future with the introduction of a mortgage system in Turkey.