How do you build an energy efficient boarding house?

[Ellie Narie]

I'd like to build a duplex with by-the-room heating and cooling. It will have a total of 9 bedrooms, which will all be heated and cooled by the room (4 bedrooms in one unit, 5 bedrooms in another). They will all be small, 100 sq ft bedrooms, and the whole building will be no more than 2,000 square feet total, which means that living room and kitchen will also be on the smaller side. Since it will need a by-the-room heating and cooling, what are some suggestions as to how to approach this? I will live in one side of the duplex (the 4 bedroom side), and I will put tenants in the other side, it will be rented out by the room, so 5 rooms will be rented out to different tenants. I want by-the-room heating and cooling in both units, as I want my family to be able to choose their room temperatures individually as well. So, each of the 9 bedrooms needs to be able to choose its own temperature, and each kitchen/living area can be counted as one area in terms of temperature control. So I would think a total of 11 mini splits should do it, and I would be buying cheap ones for $200-$300 each online. 

What are some strategies to approach this kind of construction project, so that each room is heated and cooled individually, without having too big of an energy bill? Should I get solar panels, and if so, how big of a solar system do I need for this kind of project? Or should I just stick with gas appliances? And in that case, how can I make by-the-room heating and cooling possible? 

So I guess my biggest concern is, how do I make by-the-room heating and cooling possible with 11 different zones without spending too much on an energy bill and without spending too much as an upfront cost? Is there a middle ground somewhere?

Also, what are some approaches to water heating? Should I get a tankless system? And if so, wouldn't that use up quite a lot of energy?