Building An Athority Website - Should I Create My List Right Away?

Yup create your list ASAP.

You can mail your subscribers with the progress of your website. The sooner you build your list and the sooner your build your relationship with them, the better.

People have different opinions on this, because they have different experiences of this.

The unarguably correct answer, so often provided here, is always "test, test, test" and discover what's best for your business. However, this isn't particularly helpful when you're just starting out with something new, don't really have anything to test yet, and can't even necessarily formulate the appropriate testing parameters, much less start monitoring them in a meaningful and productive way.

I strongly suspect that in reality, which method is likely to be better for you depends on what has brought your traffic to your site in the first place, because that's what determines their expectations of it, wishes for it, and the extent to which it coincides with and fulfils what those people are really looking for.

For myself, across a range of 8 different niches, I've always found (I haven't actually tested all 8 of them, I admit, because by now I've drawn some "general conclusions" about "my type of customers" and how I'm attracting them) that I do much better without a squeeze page, by showing people a content-filled site without them needing to opt in first, and by having an incentivized opt-in prominently featured on every page of the site (which, of course, is easily done with a side-bar arrangement, if you're making the site from any sort of "blogging software").

Some people have done their own testing and found the opposite (and many more haven't tested at all but have simply assumed the opposite).

I suspect, though, that some of them have "tested" it simply by measuring the number/proportion of people who do opt in with each format - a huge mistake, in my opinion: income is a much better way to test! The logic of the assumption made here is exactly analogous to the widespread mistaken assumption that increasing your click-through rate, when article marketing, is necessarily going to increase your income - and that one's just nonsense (and no guesswork at all involved in that conclusion!).

I'd rather have fewer opt-ins and higher income, myself, and I don't for a moment accept that in the long run more opt-ins are necessarily going to lead to higher income, because it depends on who those people are, what proportion of them are really potentially buyers, what's initially attracted them, and so on.

I'd suggest to you (and I adduce no evidence at all for this - here I am only guessing!) that if you're attracting people by PPC advertising, you'll do better in the long run with a squeeze page, and if you're attracting them with high quality articles, you'll do better with a side-bar opt-in, because many people attracted by high quality articles arrive at a site wanting to see a further plethora of high-quality content before opting in.

Just my perspective. And good luck!