Thats a good question, I ve looked at this and I cant believe others dont. If a development offers i.e 5% 2years, you ll in many cases be paying 10% overprice on top of your gringo price. Often they are simply giving you SOME of the 10% back. So it doesnt mean a great deal to the developer if its rented or not. When I say some of the money back I mean many would still take money of that 5% for tax, 30% commission, electric bills and communal fees even with it been empty. Basically you still end up with nothing or very little. Best to buy somewhere with infrastructure and in highly rentable areas and simple use a rental company privately then you can gain a lot more.