The Kleen is an on demand cleaning company. You can go on their site, and schedule to have your apartment/house cleaned within a day. From a technical stand point, this may be one of the hardest sites I’ve ever made. And it was all done with WordPress.
I used woocommerce to make a product and handle payments, and added a whole ton of plugins, that all interface with each other. This was to allow people to schedule different cleanings (recurring payments), add various options to their package (bedrooms, bathrooms, type) and even checkout directly from the site via a credit card (stripe).
Each variation has a different price for the cleaning types (basic, standard and deluxe), so I used custom jQuery to overlay the prices on the different options, so a user would know how much a different plan would cost.
We set up hosting with WP Engine, as well as an SSL certificate so all data (credit card processing) is encrypted at 256 bytes. This also allows the site to be speedy (the home page loads in under a second), and secure (the site is automatically backed up and updated every day).