Will Google Charge me for API Usage?

You have to provide your billing info but you receive $300 worth of credits. This is a recent Google policy change to protect against API abuse.

A scenario in which an API key is abused is an instance where a user performs search queries 24/7 from one or more computers using scripts or bots.

If you use the software normally (search for leads, send emails) normally (without using bots or other spammy practices), the chances of being charged are minimal.

So if you don't abuse the API keys you generate, you will never get charged. And even if you do, It won’t be more than a few dozens of dollars.

The amount they charge for each search query is based on each market.