Well, I had a whole new roof put on a house and it is not rocket science. The house had a flat roof. I had it removed and replaced with scissor trusses so that I had a charming roof on the exterior and a high ceiling inside. It was totally worth it.
Of course you will have to have an expert evaluate your foundation and structure to make sure they are built to support the extra weight of a second story, and you will need to do the whole permit/engineering thing.
As for the structure and work, an easy way to design it yourself is to go to a truss plant and work with their sales staff. The one I worked with had a guy with a computer. I sat next to his desk with the plans I had drawn and he popped up an appropriately-sized truss on the computer, asked me if that’s what I wanted, we tweaked it a little, and he printed out the plans and elevations which I took to the city for permits. There was no charge for this guy’s design work.
Then, after permits were approved, I ordered the trusses, had them delivered, and the carpenter installed them. As you can imagine, they go up very quickly. Now this house was very very small so a crane was not needed, but the truss plant will help you with that decision or information.
If you are interested in going this route, instead of having a custom-framed roof, you would want to look at a style called attic trusses. Here’s an example when I googled “attic trusses” in images:
https://www.google.com/search?q=attic+trusses&biw=1440&bih=838&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiH1dSfqe_PAhUFxFQKHZN_AF8QsAQIGw
You can see that there is room to tweak the slope of roof, the width of the attic space and the shape of the inside space (whether you want a partially peaked ceiling or a flat ceiling).
-More space can be designed by adding more trusses, by thickening/strengthening the wood, and/or by strengthening the joint connectors.
-Strength over and above what the code requires can be designed in. In my case, I told the guy to design everything (which he does with a few clicks of the mouse) to extra wind/hurricane strength and super snow loads. I had researched the average highs of those two conditions in my town before I went to the truss plant meeting and knew what I wanted. I want to add that these increases in performance do not necessarily cost much more. Wind resistance is augmented by requiring more hurricane clips, like for every truss instead of every other truss, which is pretty cheap. (Of course there are other design methods for this as well). Designing for extra snow loads in my case was done by adding trusses, making them on 16" centers instead of every 24".
Hope this helps for that small part of your project.