回複：家裏就我一個孩子，父母想來美國定居

To meet parents' requirement, they have to come as refugee or apply assylum and later file I-485 under those categories. In that case they can legally become public charge, immediately qualify cash assistance and still get GC. And you don't need to sponsor I-864 or anthing because it will be their independent case, which has nothing to do with you. Their I-485 fees can be waived under such basis.