I have bought direct from a mill a few times with good success, but never had them plane either one or both sides. I have always planed and jointed it when I got it home. This is the better way IMO if you have the equipment and time to do so.
He asked if I wanted it planed on one side only or on both sides. Is there an advantage of one over the other?
I can only guess that he is saying the one side planed "real nice" would be the side you would have showing in the project and the unplaned side would be hidden, not finished and not needing that much work.
"The one-inch planes to 3/4" real nice, one side. The 4/4 planes to 3/4" both sides." Anybody explain this to me? He said many of his customers have the lumber planed on one side down to 3/4" because they only need one side planed.
The wood I bought was samill sawn, not bandsawn, and the surface was rougher. I have had no bandsawn lumber but can imagine it is somewhat finer surfaces as my bandsaw places a finer surface on wood than a rip saw.
Bandsawn lumber normally needs only a light sanding even if not planed so my experience is that you'll need little more than a light sanding on the stock surfaces. The edges may need more if not put through a joiner-planer
I would select it myself so you can judge which is straighter than others and pick and choose. This obviously takes more time, patience and energy but gives you better control over what you have to work with.
He said I am more than welcome to come out to his mill and pick out my own boards or if I have him pick them out he will get the best he can for me
I took a pecan tree to this saw mill nearby and they cut and kiln dried it for me. The finished product was more warped and twisted than I imagined it would be, but this could be that the tree was not select enough for turning into wood lumber. In fact, I took two logs to him and he looked at the second and immediately declared it had too many knots in it and that his saw blade would not even go through it. This turned out to be some of the hardest wood I have worked with. In fact, it is so hard I have decided to use it for jigs and template type stuff. Being as hard, it allows me to mill and shape to more exacting standards than softer wood would. I recently made a re-saw guide from it and that worked well.
Hope this helps !
It is impossible to make anything foolproof because fools are so ingenious.