First Time I buy a property as an investment. Anyone who has done this in Tenerife who can give me advices?

Hello everyone! I am planning to buy my first property as investment in Tenerife. I'd love to own my house in Tenerife and move on day to the Island, in a quiet location, but I would need first to make some money by renting out a property, since I want a flat with sea view and many other features and cannot afford the price at the moment. So my plan is to buy a flat to rent out for some years, then sell it and but my own property with the money I gained from the sale as well as the rental income. Being the first time I do this, I would like to speak with someone who has experience and able to tell me how to manage the money and understand which proprety can give me the best returns. I did ask the agents, but they don't provide guaranteed figures, only approximate /estimates. 

Considering the money to be invested, I would rather have guaranteed figures! 

Thanks!