How to remove light mold?

[Kyle Shepherd]

So the small SFR I'm looking at purchasing in super rural Alabama has a little bit of mold/mildew (not black mold thankfully) in a couple of the rooms, on the lower half of the walls, due to poor drainage. (No gutters and no french drains.) What's the way to deal with this? Is this as simple as (1) install gutters, (2) install french drain, (3) use killz and repaint? Or do I need something more drastic?