I think that will work for now. The only draw back is the credit card option is still shown on the checkout form. This is only an issue due to the credit card fees if the student is not selected for the course. Someone will be losing out on money in the event there has to be a refund. I have placed a message above the payment area to not use the credit card until requested. But will most likely be a problem at some point, since most people don't read all the info.
Perhaps a pay later option might be beneficial where the is an option to hide the other payment methods, and or ability to login later and pay as usual.
I use Membership Pro. I followed the previous instructions but when the possibility of paying with PayPal is published, after the approval of the registration by the Board of Directors, for several days a new user would also see the PayPal system published and could use it when he shouldn't. I solved it like this:
1. in the table of payment methods put the offline method in first place
2. also left the PayPal method in the form but obscured with the css display: none
It works well, with the request email to complete the payment, the link to complete it arrives and the registration is activated and the registration summary email is sent.
I have only one problem: only the email confirming registration is sent but not the one with the invoice and the membership card.
To send them I must, each time, select the member and choose "Send mail".
Why does this happen? How can I get the invoice and card to arrive after the payment is completed?
Currently, we do not send invoice and member card in Subscription Payment Email. Need to think more about it. For the time being, could you get this file, unzip it, upload the received file to administrator/components/com_osmembership/libraries/mpf/payment folder, then check to see if it works as you want?