score:8
As the USCIS explains, your initial entry to the US in E-2 status is for two years, and you can extend it indefinitely. You are required to leave eventually, but you aren't required to have a return ticket at the time you enter.
Upvote:6
Yes. You may have to convince the immigration officer that you will comply with the conditions of your admission in E-2 status, including having the means to purchase a ticket out of the country. But in any event a round trip ticket is not required when you enter.