Hello,
My name is Rui Pimentel and I'm an expert in development of web crawling and automation tools.
I've been focusing on this area for the past 8 years and have crawled recently the biggest websites of real estate in Portugal and Brasil, as well as the international known airbnb.
I completely understand what you need, and I would develop the solution completely with simple well documented PHP, MySQL and cURL. I would be able to provide you this within 2 weeks and the price would be 1250$ + fees.
The tool would be very simple so I'm sure you should be able to do future edits if needed, but I always offer future support if needed at a 25$/hourly rate currently. If any bug comes up in the first 30 days after we settle this down, I'll of course fix it without any extra payment, unless some of the websites completely changes.
Technically speaking it would basically be a search form where you set all the searching params, and once submitted I would trigger each website search in different threads, and return the results with ajax dynamically, to give a better user experience, since the search process might take different times depending on the website.
I'll be waiting to hear from you, and hoping I can make you happy, as I did with all my past customers, I'm sure both you and your client will be very pleasured with the final result.
Thanks,
Rui