If we create free salesforce account, how many days it will valid and post free trail how much it will cost

Hi Mayur,

Free trail (recommend: developer sandbox) wont be expired. until you leverage proactively. https://developer.salesforce.com/signup

If you want to try sales or service or any other products (enterprise edition) --> it will be 30 days after that it will be expired. this product comes with sandboxes too. - https://www.salesforce.com/editions-pricing/sales-cloud/

Hope this helps..Cheers..