The stock is up over 300% in recent months, but a rising inflation rate could spell trouble. Opendoor is trying to build an Amazon-like e-commerce model for the housing industry, where people can buy and sell homes online. The company buys homes, usually those in good condition or those that only need minor repairs, then resells them on its online marketplace. It sounds like a great idea, but the company hasn't been able to turn that into a sustainable business yet. The profit margins are slim. Opendoor has ...