Yes, the vacancy tax encourages economic activity, which is the opposite of the income tax which has a side-effect of reducing economic activity. Another reason that camgunz’s analogy is flawed.

According to the plaintiffs, the problem with the vacancy tax is that the city is not supposed to force homeowners into the business of renting that they do not want (Ellis Act https://leginfo.legislature.ca.gov/faces/codes_displayText.x...). It is similar to the Obamacare individual mandate, which also forced people to enter the marketplace, which Congress is not allowed to do by the Commerce Clause of the US Constitution. But in National Federation of Independent Business v. Sebelius, the US Supreme Court said that the individual mandate is just a tax and not a compelled transaction, since “It may often be a reasonable financial decision to make the payment rather than purchase insurance, unlike the “prohibitory” financial punishment in Drexel Furniture” (https://supreme.justia.com/cases/federal/us/567/519/)