You will find many 'back of the napkin' calculations here on BP that people use to assess whether or not a property is worth looking at further.

As for the first flip, go with these margins for "napkin math" to quickly evaluate it.Buy for at most 50% of ARVRehab for at most 25% of ARVSell for 100% ARVThat will help you avoid overpaying.

Those being: safe, structurally sound, and sanitary.

@Evan Miller im looking at a deal like that right now, they have some back of a napkin financials and no T12. your best option is to make an offer based on what you have, just go at a price which make sense to you. add a clause that they have 10 days to provide you with the current Rent Roll, Financial statement Schedule E, Utilities bills, copy of the lease, deposits etc etc. 

@Drew Y. it can be something as simple as a promissory note written on the back of a napkin (not that you'd ever want to do that but it is legally binding). 

Did I also mention they seem to be hoarders (So much unwanted junk in the rear of their unit by where they saw the rat) I’ve told them verbally plenty of times I wanted everything trashed since their lease states they are to keep the property clean and sanitary clear from any debris,trash,recycling ect. 

Please don't perpetuate this erroneous definition.To be a good operator, you provide a safe, clean, sanitary, well-maintained property at affordable rents, AND you screen and only retain tenants who abide by your rules and treat the property and neighbors respectfully.

If the sanitary conditions in your unit are such that it attracts pests of any kind, and it becomes necessary for us to undergo remediation in the building, you will be held financially responsible for reasonable costs thereof, paid as additional rent.This is what I use. 

(There is no such thing as the “wrong form”... you can write a deal on a napkin as long as both sides agree to the terms and they’re reasonable.)

Lease Agreement says: Quote:CARE, CLEANING AND MAINTENANCE: Except as prohibited by law, Resident agrees:(a) to keep the premises as clean and sanitary as their condition permits and to dispose of all rubbish, garbage and otherwaste, in a clean and sanitary manner, unless Owner/Agent has expressly agreed otherwise in writing in an addendum tothis Agreement.