I have to say that the first time I heard you say you were buying a house to live in between the move from one place to another, I thought.....what ? Never heard of such a thing. Sure, I had heard of folks renting when moving a long distance while they shopped for a home to buy in their new area. I do guess it depends on how long a person would need to live in a "halfway" house before buying though. If only a few months, it wouldn't seem to make sense, but for an unknown extended time, I do guess it does. It also makes sense to live near where you are going to build especially if you are going to do a lot of the work yourself and to keep an eye on whoever is doing the things you won't be doing yourself.
Sounds like quite the undertaking. Just moving from one place to another without all that extra is quite a chore in itself. I don't envy you the process, but I know when it is done you will be very happy on the new lake.