Is there a deposit?

A cleaning fee, if there is one, is set on the listing and shown under the price before you book — it isn't a surprise at the door. Same for an extra-guest charge.

A security deposit is different. If the owner takes one, the listing shows it; they collect it and return it themselves, not through the site.

Questions about it go in the message thread on your booking, once you've sent the request, so the answer is written down where you can both find it.