Back in the mid-2000s, when money-market accounts were paying around 5%, and there were a ton of promotional 0%-balance credit-card offers, people from fatwallet used to use the term "app-o-rama" for this trick of applying for a ton of 0%-balance credit cards all on one day, so that they'd all be approved before the credit score was updated. Then, there were ways to essentially extract the balance as a cash advance w/o it being coded as a cash advance. A few cards (like Citibank's) would let you do a "balance transfer" via a check made out to you, and then you could transfer that balance to others and repeat. The end result was that you could take out a quick $50k or so in credit, put it in a 5% money-market account, and pay it all back 12 months later when the 0%-rate intro promotion would be expiring, netting $2500 interest.
You could also start a business with the cash, but that's a bit higher-risk...
You could also start a business with the cash, but that's a bit higher-risk...