1. Be a good neighbor The first place I suggest to look for cheap moving boxes are from your neighbors, especially new neighbors. If you have new neighbors, they probably needed boxes to move into the complex, and have most likely unpacked everything and no longer need the boxes. Be a good neighbor and take the used boxes off their hands.
Paring down the excess clutter will free up space in the house for a bigger, cleaner look during open houses and showings. If you have way too much stuff, you might consider having a garage sale before you list your property.