Functionality Customization Of Purchased Motor Directory theme

Hello everyone. Note: R = Rand (South Africa's currency) I need a theme customized with some special functionality, i don't mind if it's done with custom code or plugins i just need this functionality in asap. I purchased this theme: [login to view URL] I've installed it here: [login to view URL] We are creating a car directory for new and used car listings. There will be 2 types of users: Dealers (Car Dealerships & Standard Users (Private People selling their cars). The theme is self has package based pricing for users to submit listings on the website. It gives them a certain amount of posts they are allowed to make per month. However my client is not opting for this type of pricing structure. What he wants is a per listing pricing structure. Which is R2 per listing per day billed weekly for Dealers & R86 for 14 days per listing and R180 for 30 days per listing for Standard Users (which will be paid upfront) And all of this needs to be as automated as possible. Functionality that needs to be implemented: - Standard Users will need to choose between the 14 day and 30 package every time they post a listing (a payment gateway needs to be in the "add a car form") - once the 14/30 day period is over the post should expire/be deleted - Dealers rates are a standard R2 /car /day - they need a separate "add a car form" with a payment gateway that will remember their card details. - The payment system needs to be set up bill them accurately every week - If the dealer deletes their listing, they should then not be billed for that listing (except the days that it was on the website) - (I need help with this part) For example If a dealer adds 1 car on monday and 2 cars on wednesday and then sells 1 car on saturday; On the billing cycle - which is monday again - the functionality might look something like this: ((1 car x 7 days) + (2 cars x 5 days) - (1 sold car x 2 days)) x R2 = R30 (If in not mistaken, that is what would need to be billed to that specific dealer. I hope you can help me! If you can do it in a better way please do. I don't have a very big budget as I thought this theme would cover everything. If you have any questions please let me know. Thanks for reading.