Adjusting a PHP search script

I'm adjusting a wordpress theme that I purchased to build a real estate site for students ([login to view URL]). The search engine from the original script does not provide me the functionalities I need, so I would like to modify the search so that it allows to: * search by property ID (this already works) * search by a combination of the following elements: * price range (this already works) * country (this already works) * property type (this already works) * other property address info, such as city, zip-code, etc (this already works) * property availability ---> THIS DOES NOT WORK YET, and has to be implemented As you see, it is just a small adjustment to an existing script.