You only pay for ads that pay off
Google Ads operates on a CPC (Cost-Per-Click) advertising model.
It means that you only pay Google when someone clicks your ad. If your ad is running and no one clicks it, you won't pay anything.
But how much do I pay my click?
Unfortunately, there is no easy one-size-fits-all answer. The cost will depend on number of factors. Ultimately, how competitive the market is (i.e. how many others are competing for the same keyword) and your quality score (i.e. keyword relevance, click-through rate, landing page quality and overall account performance).