Famous (slightly) older people –
Harland David Sanders or Colonel Sanders of Kentucky Fried Chicken fame
Col Sanders secret chicken recipe was rejected a reported 1,009 times before one restaurant accepted it.
Walt Disney
The man behind Disney was initially was fired by a newspaper editor because, "he lacked imagination and had no good ideas."
Even after this, Walt Disney started many businesses that unfortunately ended in failure. However, he kept trying and obviously found something that worked!
Henry Ford
Henry Ford had 5 businesses prior to founding the hugely successful Ford Motor Company.
Akio Morita
The founder of Sony….their first product was a rice cooker that unfortunately didn't cook rice but burned it! It sold a reported 100 units. Obviously this set back didn't stop Akio creating a huge multi-national.