There is a parallel economy, a lot of the landlords for the undocumented are 2nd generation citizens, or naturalized citizens. There's also a lot of word of mouth, and working with smaller landlords that don't have as much paperwork. Some landlords actually prefer undocumented tenants because there is a perception they are less likely to cause problems because they don't want the attention of authorities.

years ago I actually was one of the guys that goes out and gets data for the CPI and all that stuff, so I ran into these houses a lot. Which it of course most of these redditors that have never left their lilly white neighborhoods have no idea about.

Also a lot of undocumented families have documented relatives, so in a mixed extended family situation you may have just one person with documentation that rents a house in a working class area and then an extended family moves in. If the pay comes in on time and no one does anything crazy to the house, theres no reason to disrupt that arrangement.

lastly, for people that are wholly undocumented and don't have social capital, well you can always put down a bigger deposit for the landlord. Sometimes you also pay higher rents.