If this is your first stab at building a guitar, I'd suggest a kit first or maybe buy a body and neck from someone. USA custom guitars here This a great place to start. Also, Universal Jems has kits.Here
It is hard to build a guitar correctly and there is a lot to learn. It gets easier eith practice. As far as time, it depends on the time sanding, finishing, putting the parts on and the set up.
Building from scratch takes much longer and takes more tools.
Good luck. I'm sure you'll get plenty of answers to your question.