When it comes to Tesla's (NASDAQ: TSLA) business, there are a number of things that should concern investors. For instance, CEO Elon Musk's promise of profits in the second half of this year has a major contingency: The automaker will need to more than double its current weekly Model 3 production rate in just three months.Then there's the fact that in Tesla's most recent quarter, the automaker posted its worst-ever quarterly loss.