Who knows at this point, I would be shocked it it was more than the S4...and all likelyhood is it will use less as the S4 seems to be a bit bloated in that regard.
I think I saw on phone arena it said it has a max of like 24gb which would seem like it takes around 8gb from all their software. Hope it is less though LG G2 vs HTC One - Phone specs comparison
It depends on how much bloatware/crapware Verizon and LG stick on it. As commented I would suspect a decent amount, yet without microSD that everyone seems to claim is unnecessary today you are stuck with limited storage if you like to take HD video or pics a lot during the day.