E2 for my prospspective co-founder

The U.S. (IT start up) entity must be at least 50% owned and controlled by a foreign organization or foreign national(s) from the treaty country (Korea qualifies for the E-2 Treaty Investor status). There are various tests to determine what amount of capital is considered "substantial" thereby qualifying for the E-2. For a service based company, $500K may be considered substantial, however, various factors need to be considered in the analysis and more information is needed. If you are the Beneficiary of a pending I-485, please keep in mind that once your Permanent Residency (LPR) status is approved, your nationality will no longer be considered for purposes of the 50% ownership and control requirement. With regard to processing times, please note that there are two steps involved: Corporate Registration of the E-2 entity with the relevant Embassy/Consulate, then the individual E-2 application, which typically are filed concurrently with the relevant U.S. Embassy/Consulate. Processing times vary at each Consular Office and it can take several weeks to months for the entire process to be completed. For more general information, please see: http://www.madisonpiperpc.com/wp-content/uploads/sites/4692/2016/10/e1_e2.pdf. Please note that this information should not be construed as legal advice and is meant for general informational purposes only.

You and your co-founder should consider consulting an attorney.  More information is needed about the company, your country of citizenship, and your respect roles in the company. The E-2 investor must own at least 50% of the company or be able to possess operational control. The investor may be able to seek a green card through a NIW. The processing time really depends upon processing procedure and interview availability at the U.S. Embassy. You can read more at http://myattorneyusa.com/e1-e2-and-e3-visas-overview.