Don't go the app route first. It is expensive, time-consuming, and without a proven product/market fit, probably a bad decision.

In your case, will it be a quick decision (swipe Tinder style for a Zipcar-like deal), or a long term rental with lots of legal and terms to go through?

Will your users be sitting at work, or will they be on the go, like calling an Uber?

But in my personal opinion, I hate downloading and installing new apps unless I already know what I'm getting. So if it's a new service, I definitely prefer a website to try out before downloading an app. An app is sometimes nice to have, but I'm personally less likely to try your product if it requires me to download an app.