Permanent residence is based on intent. The law does not prescribe a minimum period. Generally, you plan to leave the U.S. for over 180 days, you should consider applying for a reentry permit.

When you first obtain your EB-5 visa, after the Consular interview, you must enter the U.S. at least once within 180 days of visa issuance to establish your permanent residency. (This also starts your 2-year conditional residency period and is the date that determines job allocation for the green card for most projects.)

Evidence of intent to reside includes opening bank accounts, obtaining a driver’s license or Social Security number, paying state and federal income taxes, and renting or buying a home.

The United States resident may work overseas if required based upon the nature of the business or profession. However, all permanent residents must remain in the US for more than 6 months each year or they break "continuous residence" for purposes of applying for U.S. citizenship. Moreover, a permanent resident who wishes to apply for citizenship must be in the U.S. for 30 months of the 5 years prior to application.

Demonstrating If you plan to be outside the US for frequent or extended periods, please consult an immigration attorney.