MLS for agent not tenants in rental

MLS is used most often by agents for rental purpose. Agent helps his/her client to look for a house and charges commission to the landlord as well.

MLS is not useful for low end rentals. Even craigslist is not very useful but it's free  with nothing to lose. 

Keep in mind that a lot of working class people don't even have access to email yet. Even they do, they don't rely on computer or internet. They drive around in selected neighborhoods to see if there are any for rent signs.