... But I have to wonder if you're really up for this if you're asking such a broad question.
Maybe you need to see some plans first. There is a lot to know about this job such as spans and weight loads. Plus, are you gonna build your own trusses? And so on. This type of job will require a good deal of know-how in a lot of trades. Framing and hanging gargage doors, for example, can be a challenge. WHat about water drainage issues too?
I'm not trying to discourage you but enlighten you. Oh, and there are permits and inspections too. (If you don't get them, and your neighbor(s) see what you're up to, they may call your Municipality especially if one of them is 'mad' at you for some reason or other.) In the least, I'd get an estimate to have the garage 'blocked and roofed.' From there, you can do the finish work (inside). Let them hang the door(s) too. If you do the electrical, get a good book that addresses garages! Their use is different, in some respects, than that of a house.
Maybe others will be more encouraging. My best to ya and hope this helps.