If you have a backyard and a desire to make passive income, there is an app for you: Sniffspot connects dog owners with people with fully-fenced yards who are willing to rent their land on an hourly basis. Described as “Airbnb for dog off-leash areas,” Sniffspot has about 7,000 hosts in more than 1,500 cities in the United States, and offers their services in Canada,…