Realty Income (NYSE: O) is a real estate investment trust (REIT) that has long been a favorite on Wall Street. There's good reason for that, but it means that stock is usually pretty expensive. That said, COVID-19 has upended things for REITs and the income investors that love them. Realty Income wasn't immune to the hit. But is it still a buy after rallying 30% from its recent lows?