Creating partial payment extenstion in Magento

We are clothing rental company and we have created our website using Magento and this extenstion [login to view URL] So every product has some rent and corresponding deposit amount like Product A has 1000 rent and 3000 deposit. Now what we want that customer only pays 50% of rent (for eg 500) while booking the outfit and rest balance amount (500 +3000) can be paid from his account before delivery date or customer can select a cash on delivery also. Booking amount has to be paid by online payment gateway. 1) Every invoice should show the paid and unpaid amount 2) Should work from admin dashboard also as we work from offline stores also We need this extension very urgently