@Anonymous To add to above response, You will not be billed if you do not have any transactions. Based on the pricing tier of your resource you will be billed based on the number of transactions made for a particular feature of the bing search service. See pricing page for confirmation.
As per my knowledge, the limits of the subscription apply for resource creation. See this page that documents the number of resources that can be created in a subscription resource group. From bing service perspective, I don't think any resource creation limit is applied apart from the usage limits that apply based on the tier of the resource. Thanks!!