I am considering a purchase here and I was planning on loading the download on a machine that does not normally have network connection. is this a problem for games off of this site? that games I am interested in are from the days before internet validation or required internet connectivity to play.

No internet needed to install and play for GOG games.

Assuming you are not interested in multiplayer, it shouldn't be. If you are interested in multiplayer, it may or may not be, depending on the game.
Feel free to check it with the free games you get when you register on the site. And welcome aboard.

I don't know that they do that any more -- I think you have to manually add ("purchase" for 0.00) any games you want in your library.