1. Get a virtual phone number.
2. Build a site about any service as if you are the owner.
3. Point the phone number to someone on the 2nd or 3rd page of google, try to find someone who is running an adwords campaign.
4. Rank the site
5. Let it run until you have a couple dozen calls to the business, (I let 50 go in) then go visit the owner.(take the phone log with you.)
6. Ask for a minute of the owners time, introduce yourself as a freelance web designer, hand him the phone logs, and tell him that you have built this site, and picked his company to take the calls at random until the site was ranking. Tell her that the phone log shows the people who have come to her business thru your site, and she can check it against the phone numbers of her recent contacts. Tell them that since the site is ready for sale, you are about to sell it, or the leads from it if you wish. Tell the target no pressure, but you will be selling/leasing it out to the first taker, and then the phone number will be pointed to the new owner when that happens.
If you are worth a damn, the business will have had a surge of new customers, and not know why, or will have already found the site and wondered what the hell. If their income has shot up, Bob's your Uncle.
Or simply rent out the phone number on a per lead basis.
7. Profit.