If you as admin give users the ability to edit there ad under usergroup permissions then they can edit it. Under admin options if you give users move delete permissions then when they edit an ad they will see the delete checkbox.
Under normal operation of the program ads will expire and delete on there own.
I know that this is an old thread. Is the answer no longer valid? I want to give my users the option to delete their ads instead of marking them sold. When I go to the admin options though, I do not see an option to allow members to delete/move their own ads.