Hi. Sorr my english.
I want a new type of listing will cover all other listing types and categories except that in this type of ad people will enter the photos of the products they are looking for and the price they can pay, and the people with this product can contact the advertiser and submit an offer.
How can i do.

In fact, i can do this with listing fields : Selling & Rent and third one Buying but this scenario, I must change any listing form. And i dont know how can i make an offer form. if sale_rent key value = 3 ... where can be placed custom code.
Thanks.