Any usage beyond the free usage quota [100 queries per day] will fail if you are not signed up for billing. Once you have enabled billing, you will be billed for all requests at the rate of $5 per 1000 queries, for up to 10,000 queries per day. If you need additional quota, please request additional quota from the console.
Google will let you search the whole web, though the results will be different from those of google.com, and you can only get the first 100 results. Usage is free up to 100 queries per day, with Google-supplied advertising, after that, it's available at approximately $5 per 1,000.