Hugging Face API Limits and Pricing

I can use the open-source models on Hugging Face by generating an API key. However, when I want to turn it into an application, Do I need to use the same API key. Is there a limit to the number of API requests? If it’s not free, where can I find the pricing information? For example, if I develop a web application that integrates the text2Image model and it receives 1000 API requests per hour, is this free? If not, how much would it cost?