Tips on building your own house / granny pad? (with own labor)

I built 3 houses acting as my own general contractor. That's not what you are asking about, but I leaned some important things doing it. The most important was my estimate that there are about 10 years required to build a 3-bedroom conventional house giving a job and other obligations. The second is that to do it yourself will likely result in a divorce. This is a very tough road to follow. Consider designing exactly the house you want (it takes me about a year to design a nice house) and then act as your own general contractor hiring sub-contractors to do the actual work. Even then it will probably be the hardest thing you have done and take over a year. Getting a house up and looking good on the outside is relatively easy, quick, and cheap. Finishing the inside is much more expensive and time consuming that a person expects.

Good luck!

I've never built anything beyond Lego, Meccano and the occasional flatpacked piece of furniture. However, when it comes to "granny pads" the most important thing to take into account is what the specified granny needs, and would like, in her new pad. When my brother added a ground floor extension to the family home specifically for my mother, the two key requirements were for: an en-suite bathroom with a walk-in shower and support rails by the toilet; and to remodel the kitchen with a lower level working surface (because she shrinks as she ages) and accessible (reachable) cupboards/drawers.

tl;dr - consult the granny before you even think of laying a brick for her new pad!