The activity only happens when the house is messy/dirty.So I put a big note on the fridge saying something to the effect of "Keep the house clean and you won't see anything. 

It is your fridge take care of the problem.Joe Gore

Here's an example of a Duplex I'm looking to close on next week and what I can expect to put aside in expenses and also take in:2bd/1ba & 1bd/ba Duplex - Purchase Price $41,500Income 1 $600, Income 2 $475,  Vacancy -$90, TOTAL INCOME = $985Mortgage $220, Property Taxes $66, Management (6%) $65, Insurance $55, Water $60 TOTAL CORE EXPENSES = $466/moSnow Plow $21 ($250/yr), Lawn Care $0, Turn Over Cleaning $25 ($300/yr), Visits/Phone Calls $60/mo TOTAL MAINTENANCE = $106/moOvens $400 x 2 / 8 yrs = $100/yr, Fridge $500 x 2 / 8 yrs = $125/yr, Dishwashers $0, A/C $0, Washer/Dryer $0, Water Heater $400 x 2 / 10 yrs = $80/yr, Furnace x 2 / 15 yrs = $267/yr, Roof $8,000 x 1  / 20 yrs = $400/yr, Carpet $2 x 600sf / 6 yrs = $200/yr, Yearly Total = $1,172/yr TOTAL REPLACEMENT EXPENSES = $98/moTotal Avg Monthly Income = $985, Total Ave Monthly Expense = $670, Cash Flow = $315,  Down Payment = $8,300, ROI = 45%!

The stove and fridge were so bad I just threw them out and got replacements.

If an $800 refrigerator lasts 15 years - and the fridge is 7 years old then you need to set aside $100 per year for the next 8 years. 

Turned out it was a VA foreclosure that needed a face lift (floors, paint, fridge, AC, etc).

Off the top of my head: a drug overdose, a death, walking in on an intruder (2x), catching an intruder on a surveillance camera, pipes freezing and then bursting in cold weather, local prostitutes frequenting my tenants, water line leak to fridge icemaker that destroys a kitchen floor, the list goes on.

The difference between an illegal apartment and an office is I took out the stove in the kitchen, replaced the big fridge to a small fridge, and took out the bathtub and put in a closet.

They really don't care what color the bathroom is painted or if the fridge is white or stainless. 

The fridge was a floor model which took about $100 off the price and was still in new condition.