There are many directions you can take this business. If you want to work during hours when no one else does, you can focus on office clients. You can focus on retail businesses and keep your customers clumped into one or two blocks. Restaurants are in great need of daily thorough cleaning and can be a great source of steady clients. Perhaps you would be more interested in house cleaning. Many times with cleaning services you don't have to spend lots of money on advertising or marketing because your customers will come by word of mouth.
Digital marketing is defined by the use of numerous digital tactics and channels to connect with customers where they spend much of their time: online. From the website itself to a business's online branding assets -- digital advertising, email marketing, online brochures, and beyond -- there's a spectrum of tactics that fall under the umbrella of "digital marketing."