You still have to pay for things like social security, etc, but you don't get to collect those benefits.
Before someone says "but illegal immigrants don't those taxes!", note that they actually do:
If not, then their employer is engaged in tax fraud, which is much easier to prove and prosecute than trying to track down and check the immigration statues of each of their employees.
The US government runs a huge profit on legal immigrants (above average job creation / economic growth), and on illegal immigrants (they pay for services they cannot utilize).
You're overlooking a few things like the fact it's estimated over half of illegal immigrant households have a US citizen child and then they start drawing welfare in the child's name on account of the fact the parents did not obtain legal immigration levels of financial independence before immigrating. Also on account that some are legally able to claim EITC in tax filing, some other similar benefit factors, as well as the fact undocumented immigrant use hospital ERs and then have no documented solvent individual to bill to (their employers also less likely to provide health insurance so they end up in ER instead of regular doctor). When you put it all together the annual public benefit is close to break even but over the period of decades counts up in the tens of thousands in the negative.
I'm generally for open immigration but I'd agree that when you consider the totality things aren't set up yet to make sure enough benefits they get are shit-canned to make sure it's at least break even. Shit-canning all the benefits that pull them below zero is definitely a less orwellian way of breaking even than the ICE/CBP apparatus, I will give it that.
[] https://budget.house.gov/imo/media/doc/the_cost_of_illegal_i...
