How do I add one time fee for my membership plan?

Many of the membership plans need one-time fee. In order to facilitate this, there is a plan level setting for a one time fee. 

In the plan settings, there is a one-time fee. Just put the amount you want to charge for that particular plan apart from the Plan cost. This way,  when the person joins for the first time, he/she will pay the plan cost plus one time fee. But those who renew their membership, this one time cost will not be charged.