Long enough that a child's age and the investor's own timetable both matter. The category chosen affects the wait, because visa availability differs between the reserved allocations and the unreserved category. Current availability should be checked in the Visa Bulletin rather than estimated from another family's experience.
Category choice is also a timing decision
Three separate periods stack up. First, preparation, which for a case built on a share redemption and a matrimonial settlement is measured in months rather than weeks because of the documentation involved. Second, adjudication of the petition. Third, and least predictable, visa availability, which depends on the applicant's chargeability and on which allocation the investment falls into. Reserved allocations for rural, high unemployment and infrastructure projects were created with their own share of the annual numbers, and demand across them is uneven, so the practical wait for one can differ markedly from another. The Visa Bulletin is the authoritative place to look, and it moves. After that comes a two-year period of conditional permanent residence, ending with a petition to remove the conditions that must show the capital was sustained and the required jobs created. A family with a sixteen-year-old should map the whole sequence against his birthdays before choosing a project. The filing used to remove those conditions is Form I-829.
Hypothetical example: a theatrical-rigging supplier has a seventeen-year-old daughter and is choosing between projects with different visa-demand profiles. An initial review should yield a dated sequence: source-of-funds collection, petition preparation, the applicable Visa Bulletin category, immigrant-visa or adjustment steps, and the removal-of-conditions deadline. The document that settles the category question is the project's location and designation evidence, not a sales presentation; the document that settles the family's timing risk is the current Visa Bulletin against the minor's birthdate versus the filing schedule. After conditional residence begins, calendar the window that opens ninety calendar days before its second anniversary for the I-829 petition. What goes wrong is treating petition approval as case completion, then discovering too late that records of sustained capital and job creation were never requested from the project. Ask who will provide those records, in what format, and on what timetable before investing.