A contribution does not itself create derivative eligibility. Eligible derivatives are assessed through the applicable relationship and individual rules, not simply because someone supplied funds.
Keep the donor and accompanying family roles separate
A qualifying spouse and unmarried child under 21 may be eligible, subject to applicable CSPA analysis and visa availability. Eligible accompanying derivatives need no extra principal investment merely to join. Do not describe every financial supporter as an immigrant family applicant.
Age matters more than families expect, because a child who turns twenty-one before the relevant point can fall out of the derivative class altogether; track each child's date of birth from the start rather than discovering the problem at interview. A filed petition confers nothing, so a family cannot rely on it to justify living in the property, and a household member already lawfully present under some other basis remains governed by that basis rather than by the investment. Two questions deserve specific advice: how a delayed arrival would be assessed for a child approaching twenty-one, and whether any period apart affects the route the household has chosen.