U.S. stocks aren't in a bubble - at least not yet, according to a team of analysts at TS Lombard. While stocks are certainly looking frothy, they're missing one key ingredient that has been abundant at practically every preceding bubble peak: leverage.

OTC stocks have less trade liquidity due to low volume which leads to delays in finalizing the trade and wide bid-ask spreads.

If you go with a real-world full-service brokerage, you can buy and sell OTC stocks. The broker will place the order with the market maker for the stock you want to buy or sell. Bid and ask quotes can be monitored constantly through the Over-the-Counter Bulletin Board (OTCBB).