Can't say I've ever seen anyone make $1M from next to nothing overnight (outside of the share market), but I did enjoy a 15% gain in 3 weeks on a property deal.
We bought for a good price and settled a week before Christmas. Moved in on Boxing day and started furiously on a cosmetic renovation. Fairly simple stuff, paint, carpet, lighting, window dressing and some general repairs.
Moved out 3 weeks later, had the property revalued and a depreciation schedule performed. The same lender gave us an increased valuation 15% over the purchase price (on a full valuation). Depreciation report calculated the 5 year write offs at 3x what they'd cost, it paid for the renovations in actual tax refunds over the next 5 years. We also got a 39% increase in rent on the previous tenants.
We've still got that property, it's enjoyed an average of about 11% capital growth per annum since we bought it, but I suspect a lot of that was in those first 3 weeks.