Immigrants both legal and not will also typically live many working adults per household. Most Americans want to live in their own from the get go and many struggle for years. The immigrants like the Vietnamese people I worked with combined incomes to reduce housing, food and car expenses, which allowed one of them to go to trade school or college, then when they work they lend money to others to get a car or go to school. Strict culture to pay back family/friend loans. Literally a group bootstrap effort. That is why they are willing to work lower paying jobs.
I guarantee if some of the $13/ hr labor jobs paid $20/hr there would be shortage of Americans willing to work them. Corporate America and farmers wants to pay third world wages domestically so you have them as major lobbyists for illegal and legal immigration. Plus you have the green card slave labor pool for skilled tech jobs.
We need to have a planned immigration inflow that does not dramatically depress labor wages. Then strictly enforce borders and visa over stays.

