According to Parkopedia’s 2017 Global Parking Index, the most expensive cities in the United States to park are New York, Boston, San Francisco, Washington, D.C., Seattle and Chicago. Abroad, it’s London, Zurich, Amsterdam, Sydney, Hong Kong and Tokyo. Top average rates are about $600 a month in New York and London, $47 a day in Sydney and $33 for two hours in New York.

Moreover, the value of parking spaces tends to appreciate even when the overall real estate market softens. Experts say this is because of an ever-declining supply brought on, in part, by developers who have successfully lobbied municipalities to do away with regulations to build sufficient (if any) parking and urban planners who advocate limited parking to encourage the use of mass transit.

Of course, the barrier to entry in some of these markets is substantial. In Hong Kong, prices for spaces can go as high as $644,000, which can make any derived rental income seem piddling. But if you’re strategic and pay attention to population density and traffic flows, you can find affordable, income-producing parking investments on the fringes of major markets, as well as in smaller cities and suburban areas, said Charles Cridland, a founder of YourParkingSpace, which he described as the Airbnb for parking in the United Kingdom.

The vast majority of listers on his platform are individuals, including his parents, who invested part of their pension in three spaces in garages near train stations in the Putney and Brixton neighborhoods in south and southwest London. They paid a total of $73,000 and are getting around a 7 percent annual return, mediated by their son’s app, which books the spaces and collects the rent.

Most individuals listing on YourParkingSpace rent out their spaces by the month, Mr. Cridland said, because it’s easier, particularly if there is a fob or card-key entry that needs to be handed over. But he said, “We also have mini-entrepreneurs who go around to friends and neighbors and ask, ‘Can I rent out your space?’” and then list maybe 20 spaces around London, some of which they can turn a couple of times a day to earn a “significant side income.”

SpotHero, an app that helps car owners locate spaces in the United States and Canada, lists mostly excess vacancies in hotel garages. But Larry Kiss, a founder of the company, said he has noticed more independent listers offering spaces on the site, whether it’s an extra space in their home garage or driveway or a space they have purchased. Another app listing an increasing number of one-off parking spaces, as well as storage space, is Spacer.