Firstly, thanks to Mark for posting my response for me. I am back and able to respond directly now.
I also wanted to reply to Martin’s question. Martin, as per my response, there is no 3,000 € tax relief unfortunately, so don’t add this into your calculations. Another downside to buying property in Madrid for short-term rentals is that the regulations for holiday rentals introduced last year, put a minimum five day stay into the equation. And with this you have to bear in mind that the average stay in Madrid is four days. A convenient little caveat helped along by the regional hotel industry.
However, there are lots of financial benefits to owning a holiday rental, as long as you buy wisely and run your business professionally. If you need any help, do get in touch.