Professional portfolio management has long cost too much. If a new company has its way, it could be free.

This past week, WiseBanyan, an online-only investment adviser, publicly launched a service that builds and manages diversified portfolios of exchange-traded funds for nothing. There is no minimum account size; nor is there any fee to sign up, to buy the funds or to hold them (other than the underlying expenses of the funds, averaging less than 0.14% annually).