How to connect paypal for Os property

I want to integrate paypal with addproperty feature of the osproperty component. Here i don;t need membership plans. and just need only ,when front end user is filling the addproperty form and there after it should display the paypal interface with predefined amount just like shopping cart system. Here payment page should be prompted just after filled the form by the user. I attached a photo like that i need to be required. How to do it?