This, as Robert VerBruggen presents it on National Review Online, certainly seems reasonable:
Trump plans to better enforce the federal law saying that immigrants can’t come — and can’t get permanent residency or a new visa status if they’re already here — if they’re likely to become a “public charge.”
Basically, the proposal would broaden the public welfare programs that would count as, umm, public welfare programs when determining whether to accept or extend the stay of immigrants to this country. For those already here, more than six months of reliance on welfare programs would count against one in the application process — not as a decisive on/off switch, but as a consideration. Currently being over 250% of the official poverty line (which basically upper-working to lower-middle class) would erase the “strike.”
It’s one thing to have more or less open borders when a person’s presence in a country doesn’t legally obligate others to provide support. With an expansive welfare state, a country has to reassess.