If it is primarily the oil spots that you are concerned about you can use a detergent, as well as concrete cleaner, baking soda, or hydrogen peroxide to try to remove them. 

Thanks a lot Dion, you almost made me spray the soda from my mouth reading that funny comment!

Think of a soda can upside down, open the top (now on the bottom) and the liquid kind of chugs and gurgles it's way out.

I spilled soda and I'm waiting to borrow a mop.I was listening to PodCast 63 today with J Scott (it won't let me @ him) while at work.

This may be the case with your neighbor, especially since it appears you've been monitoring the supposed activity the neighbor claims and seen nothing that confirms this.Some home owners are just nosy people who would rather see an empty building than tenants living there.My story....we once had an incident where a young man decided to ride his bicycle down to the local Kroger very early one morning to buy his uncle some soda. 

The market forces of supply and demand tends to always win out in the long run ... doesn't matter if you are talking cans of soda pop, drugs, or housing.

Soda Machines, Laundry Soap Dispenser, Arcade Machine, Candy Machine!  

One restaurant in the ghetto will serve you a hamburger, french fries and a soda for X dollars.Another restaurant in a nicer neighborhood serves you a steak, baked potato and a glass of wine for less money.Motels are the hamburger place, I'm the steak place. 

. $350,000 at a 15-16% (projected) cap rate with room to expand the net a few ways (storage units, coin laundry, coin laundry detergent dispenser, delete the cable that is included in their rent *never heard of that one*, possibly a soda and candy machine in the laundry area since there is no convenience stores nearby etc); With all of these changes I'm hoping to push it to a 18-19% cap rate. 

Try spraying with muriatic acid solution to etch the brick and clear up some (more) of the ivy damage, then power wash with a baking soda solution to neutralize the acid and stop the etching process.