In the year 1999, and around three years following, I received a steady income of $600 per month for 5 minutes per month. Here is how I did it.
In the winter of 1999/2000 Yahoo was flying high, on the tailwind of Geocities and Broadcast.com acquisitions (for around 10 billion). Around that time, Yahoo decided to get into personal finance business. There was talk of Yahoo buying a bank.
I received a Yahoo-branded credit card offer: pre-approved $25,000 limit and 1% cash back. It so happened that I needed a backup credit card, so I took the bait and signed up.
Very shortly I received the VISA card. And then another. And another. Each of the three cards had a different account number. I activated all three. It appeared I now had $75,000 in credit.
To simplify, I called customer service and told them I had three accounts which I wanted to consolidate into one credit card. They were happy to help me, and in a week I had a single high-limit credit card. The limit was reduced to $65,000 in the process, but whatever.
Along with the new card I received 3 checks to tap my credit line, with no fees attached. I read through the agreement, and to my surprise, the 1% cash-back applied to any kind of spending. What the hell, I thought. I wrote myself a check for $64,000 and deposited into my account.
When the statement came in, I paid the $64,000 bill, and netted $640. I got three more blank checks. Over the next year I continued the process, enjoying the ride.
At some point in 2001 someone at Yahoo figured it out - I am sure I was not the only one doing it. They imposed a cash-back maximum of some sort.
I am a hacker, so I dug into the details of the Yahoo account agreement and promotional offers. There was a cash-back limit now, but they still offered 1% in gift certificates on all purchases and cash advances. I certainly did not need $640 a month at Bed Bath and Beyond, but one of the vendors was Giftcertificates.com, an aggregator of gift certificates, which could be exchanged for any number of different stores' gift certificates.
Giftcertificates.com became my cash-back method for many months that followed. As a new parent I found many places to use my gift certificates - drugstores, children's clothing stores, bookstores, and the new company with a weird name, Amazon.
Another year passed. Now Yahoo was in the toilet, and had sold their credit card business to some other bank, which decided to close the loophole by imposing a 1.5% charge on checks drawn against the account, making the 1% return unprofitable. Once again I had to put on my thinking cap.
At that point the US Treasury department introduced a new website which allowed you to buy US Treasury Bonds, and they took credit cards with no fees. For the next year or so, like clockwork, I purchased treasurys, continuing my uninterrupted income stream.
I can't remember the exact details of how it ended, but I think the new bank noticed that my only spending was a single $64,000 bond purchase, and cut my credit line to just over $10,000, citing administrative changes.
By then I was thoroughly bored by the whole thing, and had other things to do. And so the gravy train dried up. I figure I walked away with $20,000.00 or so - not too bad for writing a check once a month.