Forms limit of free account

I also need to create a new form is there a charge for this or should I just substitute one of the older forms I no longer use

You are free to create an unlimited number of forms on the free account. There is no need to delete the previous forms you no longer use especially if you know you might re-use them in the future.

There are other limits of the free account you can view here: https://www.jotform.com/pricing