Many millionaire-making stocks weren't obvious winners at first. Tesla almost went bankrupt years back, but that would have been the best time to invest as the stock generated life-changing returns over the following years. Upstart Holdings (UPST -3.39%), which uses artificial intelligence (AI) to evaluate consumer creditworthiness for loans, could be at a similar fork in the road. The business is fighting extreme adversity, but there is an undeniable upside if things work out in the long run. Don't get the ...