6 ft large-format printing machine” you mean a printer that can print roughly 6 feet (72 inches) wide, there is an important distinction: the common commercial class is actually 64 inches (about 5.3 ft / 1.63 m) wide, while true 72-inch machines are less common.
For a sign/advertising business, the 64-inch class is usually the practical choice.
What a 64-inch machine can do
A modern 64-inch eco-solvent printer can produce:
Banners and flex
Posters
Vinyl stickers
Vehicle graphics/wraps
Shop signs
Wall graphics
Backlit graphics
Window graphics
Floor graphics
Outdoor advertising
Labels and decals
For example, the Roland DG True VIS XP-640 accepts media up to 64 inches wide and has a maximum printing width of 63.5 inches. It supports 4-color CMYK or an expanded 8-color configuration, with resolutions up to 1,800 dpi.