A good agent can not only point out things you might not notice/know to look for in the experience, but also should help lead you to strategic advantages.

Also, there is the issue of the legal ST rental regulations, which can be an advantage compared with the US or not. 

So a passive investor could not take advantage..

After a year of stress and headaches, he sold it off and swore never to invest in an area he didn’t know again.From what I’ve read in the Wall Street Journal, investing locally gives you a huge advantage because you understand the market firsthand.

Would that be an example of a "guru" taking advantage of people?

With your experience I'd think you could do great in either, but you will have a big advantage in the asset management portion of the investment which is huge. 

You don't say where you are located....but a big advantage of the mini-split is that it can cool the unit as well as heat it.

Working remotely can make be very advantageous for REI since you'll have a little more flexibility. 

Besides land, infrastructure/site work, and the building construction itself, am I missing any other major category of costs?

The former provides a much lower return on equity but is simpler and easy to achieve over the long run.The latter is much more time consuming and risky, but provides high returns and a lot of tax advantages.