how long is a piece of string?
I know its an unhelpful answer, but a majority of people on here would agree that the amount of time varies depending on your budget, time to put into the project, your desired finished product, how much work you do as opposed to buying parts ready made, etc....
As a first build, you should maybe consider buying a ready made neck. Necks seem to be a difficult area to master and if you didnt know about neck angle, I doubt youll know enough to plunge in and make a whole neck with no problems. The advantage of ready made necks are also in the time it will take to build your guitar. You dont have to build it, shape it, install a truss rod, add the fingerboard, fret it, add inlays, etc.... you just bolt it on.
maybe you do feel like having a go, and thats great. I wish you luck and would love to see the finished product, but bear in mind, if you ruin it, its the cost of the materials all over again and longer timescale to get your project back on track.
still, go for it if you feel competitant!