classifieds plugin

Hi i would like to make a classifieds section on my website, everything goes fine but there is only one problem.. its gonna be like without payment, just listing.. and adding to listing will be done by logged in subscribers.. not by only admin. because i want people to add their used items and sell them on my website .. and i also want people to be able to comment under the products. so they can comment to product that they are going to buy money transfer wont occur by website.. just people will add and sell their products.. .. so how can i change classifieds plugin like that ? or is there another plugin like this ?