Update...
So after one of the Flippa auctions closed, I reached out to a seller and asked if he would be willing to sell me his marketing plan for $xx. He agreed and sent it over.
Here's how he was able to invest so little into PPC for a great return:
The seller basically bought Visa/Amex gifts cards online and used them to set up new Bing accounts. By opening a Bing account with a credit card, he was automatically given a new advertiser bonus credit. Therefore, he would be adding $50 to his Bing account but he would get an additional $50 from Bing for signing up. As a result, he could bid $1 on his CPCs because the bids would really only cost him $0.50. That's exactly how he ran his sites: create credit cards, load them into a new Bing account, create and run campaigns, delete the account, and repeat.
The downside? He said he had to delete his campaigns and account every few days and start all over again, just to stay under Bing's radar. There were a few other steps involved (creating new email addresses, etc) but you get the idea.
It sounded shady as fuck. I mean, this is from the guy who sold me his website marketing plan even after someone paid like $2k for his auction. Not sure what I was expecting, but I never bothered testing his stupid tactic.
Moral of the story: Be really cautious buying on Flippa. I didn't care about spending $xx to see his plan, but I would be fucking livid if I paid thousands for that shitty marketing plan and a one-page website.