One of the hottest home improvements right now is upgrading or installing new gas fireplaces. Most newly installed fireplaces have on thing in common: they require a mantel to suit the fireplace. Building and installing custom fireplace mantels is a great business to start for a person who has expertise in construction, or more specifically, cabinetmaking. This sort of business can easily be started for less than $1,000 and be operated right from a truck or van. In terms of marketing the mantels, there is an endless supply of potential customers who can provide you with work, including homebuilders, interior designers, renovation companies, gas fireplace retailers, architects, and utility companies.