Garagekeepers legal liability covers damage to a customer's vehicle while it's in your care, custody, and control. The legal concept behind that phrase is bailment, and courts in most places treat a self-park lot where the driver keeps the keys as a license to park rather than a bailment, which is why girder is right that the coverage often has nothing to attach to. Whether a particular arrangement creates a bailment is decided under your state's law and the facts, so confirm with your broker in writing that they've rated it as unattended self-park and ask what they'd need if you ever added an attendant.
What a lot like yours normally carries is commercial general liability, which handles the slip and fall in the aisle, and property coverage on the physical improvements, the kiosk, lighting, fencing, and signage. Many owners add an umbrella over the general liability because parking claims are bodily injury claims and those are the ones with tails.
On licensing, this genuinely varies by state and often by city, since some municipalities license parking facilities specifically and also levy a parking occupancy tax that you collect from the driver and remit. Call the city's revenue or business tax office rather than relying on the website, and ask directly whether a parking tax applies to a 25-space unattended lot, because getting that wrong accrues against you month after month.
The expense that surprises small lot owners is lighting and its maintenance. Poor lighting shows up in liability claims and in your renewal pricing, and a pole knocked over by a truck is a real repair bill.
