The main issue is local council and getting permit to build the house first (be in Bungalow or long house).

Even you own the land, it doesn't make you or allow you simply build a house without local council approval. Authority has the right to tear your house down because of it.

Whethe the sewage system, water, electricity etc cost being taken account, I don't know, but they must be in place.

It is best to clear one by clear (getting approval etc) before taking next step of looking on ROI. There may be lot of hidden cost which cannot be seen until you start to build it, or rent it out.