Question: who's going to build your new home (frame it, drywall it, texture it, pour the concrete, and roof it)?
Answer: The same lawful people who do that work now. (I know lots of them.)

Not everyone, including the employing homeowners, hire illegal immigrants-it's kinda against the law to do that. Hugely actually under 8 U.S. Code § 1324a - Unlawful employment of aliens
 
(Maybe if I add this my post will stay up lol!) 
"Penalties for Employers Hiring Illegal Immigrants"
https://www.legalmatch.com/law-library/article/penalties-for-employers-hiring-illegal-immigrants.html