The worst property we bought was an $18,000.00 'Wrecking Ball Special' which had not been taken care of and vandals had painted on the outside, thieves had broken in and stolen things but not the wiring luckily. We did quick inexpensive fixes and rented to a low income person who applied for weatherization and the program put in new double pane windows, a new cooling system and insulated the attic. We keep gradually improving it and when the low income person moved on (she bought a home) we re-rented at a slightly higher rent and still keep slowing improving it. It has been positive cash flow for us. We bought it using insurance funds from a previous rental that burned.
What do you mean by "worst property"? The property in the worst condition or the worst deal?
I bought a hoarder house a couple years ago for $55,000. I spent $20,000 fixing and cleaning it. Now it's worth $153,000. It was a terrible, no good, very bad house but it turned into a great investment.
The worst property I've ever bought is the jumped-up white-trash townhouse condo I currently live in up in the northern suburbs of my city. I did not select this property. I overpaid for this shoddily-constructed hovel with its HOA fees and idiotic rules, utterly incompetent and corrupt management, and neighbors I still would not be able to sit down and eat with if I hadn't had a meal in three days.