ERP next Hire purchase module

Hi, I need to create module for Hire purchase sales with hire purchase sales invoice, purchase invoice and payment entry with some custom fields and some conditions when user select some options in the form in ERP next. Sales Invoice- Hire purchase Step one Create customer in quick add form with below details Customer ID must be unique and searchable in sales invoice, payment entry, journal entry etc.. (mandatory field) Customer Name (mandatory field) Customer address (mandatory field) Customer contact number - (optional) Sales partner (must be fill according to log in user and eligible to change if needed) (mandatory field) step two -Select item to be sold select price list (sales invoice numbering series much be change based on price list) select item auto select payment term based on item ( EG- item group A eligible only 30 days and 60 days, Item group B only eligible 30 days and 90 days etc..) Need option to configure. Step 3 Guarantor creation (there are max two guarantor per item. some item has one guarantor some item has two guarantors) Guarantor ID must be unique and searchable in sales invoice, payment entry, journal entry etc.. (mandatory field) Guarantor Name (mandatory field) Guarantor address (mandatory field) Guarantor mobile step 4 advance payment entry- Amount not less than 20% of the sales amount plus one installment cash accounts must be auto select based on log in user and ability to chase if needed. amount ( must be not less than 20% of sales price plus one installment based on payment term) Save and submit then print in half of A4 and full A4 separately. two printing template. Payment entry (all below fields are mandatory) select customer name based on name, sales invoice # and ID number select mode of payment auto select cash account or bank account based on user log in display customer invoice details with due amount, total outstanding, payment history , item serial, name, expire date and ------------------------------------------------ Balance due as at the date (this will calculate as if the customer settle total due within 30 days charges like interest, service charge and insurance deduct from the total due amount, within 60 days only deduct service charge , more than 60 days include all charges but interest should calculate based on no of days when the settlement occur) on the payment entry form Check box to click for early settlement option. if this clicked, amount field must be fill with early settlement amount and no other amount authorized. ----------------------------------------------------- enter amount auto apply to due amount save and submit then print in half of A4 paper. Purchase invoice- just added accepted warehouse at the beginning. I need those modification to apply to any company file which I will go to create in future as well as now. Please send you time frame to finish this project and if you done with excellent performance and low budget I am looking for long term work relationship with you. Send me your feed back.