At just $8 per share, Archer Aviation stock is cruising near its lowest altitude in a year.Every now and again, a start-up becomes a household name overnight after it raises a huge round of funding from top-tier venture capital firms and achieves unicorn status -- that is, a valuation of$1 billion or more.When this happens, it's common for investors to wonder how they could have gotten in on the action. Unfortunately, investing in start-ups is off limits for most people. Unless you are an accredited invest ...