Hi, very interesting project !
Based upon my experience this can easily be achieved.
My suggestion is to divide Your app from the 'scraping engine', so the database of ads - text, phone, name, address, photos and e-mail will be built from a pure webservice that can act as a parallel concurrent aid.
This way You have speed, data an if is needed even A.I. to help scraping.
Feel free to contact me for any clarification or question that can get the success of your goal
Cheers
Gianni