They know divorce attorneys, senior housing nurses,

funeral home managers, etc so they have all the leads to find cheap houses. 

I receive leads from them daily, though only buy or let my clients buy four to six properties from them each year. 

One extreme case - the deal hunter signed contract for $120,000.  I bought the contract for $40,000. Then I sold the house for $220,000. I just replaced the lock and did not do anything else.