As a generality, we can say that you need mild winters and not too hot summers, so a latitude of 40 - 50 is good.

To go further, we need to know more. 

What size of boat? A live aboard takes 1-4 years, at least. Where have you residency rights for that amount of time?I wouldn't advise anyone to build bigger than 20ft as a first project, there's simply too much to learn. If you employ others, you become the project manager, and need to know more than they do, or you'll get the boat that they want to build, to their standard, not necessarily what you had in mind.

Why build? The only valid reason these days, with so many secondhand boats that cost less than a new build, is that you know precisely what you want, and it doesn't already exist.

Where do people think is the best location in which to build a plywood/epoxy boat these days? I am a neophyte builder, so rather than trying to work things out slowly on my own, I am considering relocating somewhere where I can hire some skilled help to speed things up. But where should that "somewhere" be?

When I look at it, the places where labour is inexpensive tend to be remote from where the materials would have to come from, so the labour savings would tend to be spent on shipping and duty instead.