As far as your structure, yes you could accomplish this quite easily. Most hosts allow unlimited sub domains so setting this up wouldn't be hard. As far as searching, you could use Google Custom Search and tell it what domains to search so that would accomplish that part very easily. You would just paste the code Google provides on your pages and it will search the content you want.
A lot of members here use and recommend Hostgator and BlueHost and they do allow multiple domains but in your case you'd only need one. In your example, autos.com is the main domain and ford.autos.com would be a subdomain. So only one domain is required in your example.
As far as building your site, you could use WordPress to accomplish this layout or perhaps even consider Joomla if you need something more advanced functionally. Nevertheless all of this could be accomplished with the right plugins, layout, etc.