Customising Project Bidding Theme - Add Monthly Subscription

I need help in changing the current setup where project owners are charged a listing fee per project listed and instead charge a monthly fee for listing unlimited projects per month. Again, bidders are currently not charged and I want that changed so bidders are charged a monthly fee for unlimited bidding. This therefore means, both project owner and contractor will be charged a fee for unlimited use of website each month. My website is [login to view URL] Only experienced coders must apply. Must provide proof of previous work done. No third parties wanted, I deal directly with coder.