Wall Units: If you have a big enough garage, wall units for storage can make your garage a great selling point. This can be a project you do yourself for a few hundred dollars. If you are not a do-it-yourself sort of person look for options that don’t have the look of interior cabinetry. Select cabinets that look like they belong there. The cost for garage cabinets ranges from a few hundred to a few thousand dollars.
If you're planning to maximize the space, add useful features, and otherwise make changes that are likely to appeal to a majority of homeowners, your renovation may end up being a worthwhile investment in your home's resale value. However, the quality of the work matters, especially if you're planning a major change such as converting the garage into a bedroom. Trading your garage space for a poorly insulated "bedroom" with no windows and the garage door intact won't do much to boost resale value.
Like wood stains, masonry stains are less viscous than paints. They soak into the masonry and don't form a film the way paint does. Unlike film-forming coatings, stains won't make your garage floor feel like the deck of an aircraft carrier. Because of this, stains are somewhat more forgiving and easier to apply and reapply as they wear off and become dirty. One of the oldest (perhaps the oldest) masonry stains available is H&C, now owned by Sherwin-Williams and sold at local paint stores. This venerable brand has been used in the Southern U.S. for many years. It's available in a wide range of colors and it can be tinted to any color you prefer. It's available in two formulations: a solvent-base (that is unavailable in California) and a waterborne acrylic available nationwide. The solvent-based formulation is the tougher one, so if you have both available, choose the stronger route unless you're very sensitive to solvent fumes.
If the concrete slab in the garage is the problem, there are more cost-effective solutions than a concrete mason. Most cracking, flaking, stains, pitting or wear can be easily fixed by calling a concrete specialist to apply either an inexpensive epoxy or polyurethane-based coating. These seals are very durable and can make your garage floor look brand new.