You spend your life and all your savings on an amazing writing tool. Unfortunately, the product is not new and is known as a "pencil." Spend "retirement" reading Zen And The Art of Valet Parking.
Your design for a pencil holster actually takes off for a minute. You sell a few dozen right out of the gate and sell the rest at a garage sale.
Your new single-wheel roller skate is picked up by TV Brands and gets prominent time slots during infomercial overnight schedules. You see steady sales and can now afford a bigger house, a new car every year, and an annual vacation to a secret island (the one place you know you won't see your invention and can relax).
Your new video game, Crabby Fire Ants, becomes a viral success and you sell the rights to EA. You make enough money that you, your family, all subsequent newborns for the next 10 years, and your entire neighborhood can retire. When that gets boring, you retire from retirement.
Your new operating system, "Doors," replaces Windows. New computers with your OS are sold for $10,000 apiece but they never have to be upgraded. You're a little embarrassed when you tip the valet with currency bearing your likeness.