What is the best option for an unmarried, adult India-born applicant to get permanent residency in the U.S. – EB-5, E-2 or family sponsorship?

Presently, there is a unique opportunity for Indian nationals to file concurrently under the new EB-5 program and that would be his best bet, if he can qualify and meet all requirements. The E-2 is a work visa and does not lead to a green card, and the F2B category is terribly backlogged so you can expect a ten+ year wait and if he gets married before his parents naturalize, the petition is automatically revoked.

Based on the info provided, it seems EB-5 through HIS OWN company would work best given you said he is an entrepreneur and intends to establish a company in the US.

The E-2 would be the best option, even before applying for the family petition. When a person applies for a family petition, that person is already demonstrating that he/she has the intent to become a U.S. resident. Any efforts to apply for an E-2 visa or any other non-immigrant intent visa are thwarted if a family-based petition was already submitted. If your son gets married and you had already petitioned for him, the marriage application would be a new one and he would acquire the green card through marriage. In that case, the case where you petitioned for him should be withdrawn. In our opinion, the best option for your son would be applying for an E-2 first, then applying for the family-based green card. Or, considering applying for the EB-5 as it would be the faster way to obtain the green card.