I think it would be helpful to have an online application with an option of deferring the membership fee until the applicant has been approved for membership.
This would allow them to complete an application, which would enter the system as a Pending status. Once they have been approved, and the record is marked as Approved, then they would receive an email requesting that they then pay for the membership.
Our group has certain guidelines that must be met for membership. There are also other documents (proof of insurance, etc) that must be sent in for review. Once these items have been verified, then they can become a member. (Another requirement is that they've been in business at least two years).
In this case, there is a possibility that someone would apply and pay, only to get denied membership, requiring us to refund the payment.
ON ANOTHER NOTE - it might be nice to allow them to submit files with the app, such as the insurance certificate, etc.