Hi @Asif Ali Kabiruddin Rajani
Being a non-resident, I only invest in short-term rentals because, given my current situation, it's the only strategy that's profitable enough and not too risky. Problem is that European countries like Portugal and Spain are following (or preceding) the negative STR regulations that you find in more and more places in North America. Even areas that we deemed safe aren't anymore. You really need to buy the right kind of property in the right place.
I'm not sure what you mean by type of broker. I find properties myself or use personal connections. Because real estate agents aren't going to play buyer agents for foreigners that maybe are going to buy, unless you're high net worth and looking for expensive properties. Moreover, in Spain for example, anybody and their mother can be a real estate agent as the profession isn't regulated. As a result, many do it more as a hobby and aren't really helpful. And you'd also need where to invest because, even if you take a "homogenous" market like the Costa del Sol, most agents will only cover their little city.
@Erwin Groenendijk, you are correct but Americans should be able to credit their taxes paid in Spain against their equivalent US taxes courtesy of the treaty for the avoidance of double taxation between the two countries.