I'm updating a site I've managed for a while on behalf of a client. They currently have four subscription plans and as well as increasing the price they want to offer subscribers the option to make payment in two stages. The reason for this is that the subscription fee includes participation in a real world event that takes place in May. The subscription fee is substantial and they don't want to put people off subscribing early, say the previous September, when the event is still six months off. So the idea would be to have people subscribe and pay a small upfront fee to gain access to the site and post their details, then the balance a few weeks before the event.
Can this be done and, if so, what's the best way to approach it?
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