It is good advice to mill only the stock that you need for a project. The trade-off, however, is reduced efficiency, as you have to repeat the machine set-up for every small milling job. I prefer to mill my rough lumber in bulk, preparing enough for several projects.
For edge-jointing, I use my table saw. The only other machine I need to mill my wood is a thickness planer.
No Jointer? No Problem
Flattening boards wider than 6” or 8” is quite a challenge unless you own one of those 12” wide jointers. For hobbyists with limited budget and space, a wiser choice is to invest in a well-built 12-1/2” or 13” bench-top thickness planer and use it both for flattening and planing to thickness.
First, I sort all the boards into groups according to their rough thickness (boards that are too long can be crosscut to more manageable lengths) and condition (twisted, bowed or cupped). By milling boards of similar thickness and condition as a group, you have to make fewer machine adjustments.