Robinhood Markets Inc. has agreed to acquire custody and portfolio management platform TradePMR, in a move the online brokerage aims to appeal to a broader group of wealthy investors. The deal - which involves about $300 million in cash and stock - is expected to close in the first half of next year, Robinhood said in a statement. Through the acquisition, TradePMR's registered investment advisers will have access to Robinhood's clients, who will also be able to easily connect with registered investment advisers (RIAs).