There is that old back of the napkin math that tells us that 90% of normal MLS properties (non-REO, non-pre-foreclosure) sell for 10% off asking (of course, this is in markets that are not hyper where bidding wars cause contracts to go over asking price - like DC).

Per my lease agreement, it states under my "Property maintenance" section -  "Tenant shall deposit all garbage and waste in a clean and sanitary manner into the proper receptacles and shall cooperate in keeping the garbage area neat and clean..." 

@Andrew Syrios is correct, particularly in the City of Kansas City, where some combinations storm/sanitary sewers are over 100 years old.

I am a broker representing myself, as such I can write an offer on a napkin if I want.

I have used spread to track stuff... but for the most part deals can be analyzed on the back of of a napkin.  

Super glue the change left for a tip on the bar/table.Take a napkin and place over a glass of water and tip the glass upside down on the table quickly setting it on the table.

These are back of the napkin calculations, and should only serve as a general guideline not a sole basis for buying.

I have even received a contract on a single piece of paper and the assignment of contract on a napkin.

Using a back of the napkin analysis, I looked for a cash positive flow and then ask "how much vacancy can I tolerate and still not go negative" - aka break-even point. 

We have had some "back of the napkin" discussions about initial funding.