Don't forget you have to pay income tax on your profit and if you bag $10,000 before taxes I would rather wipe table at Taco Bell rather than spend my time and take a risk when there are so many unknowns.

Knowing when to let go e.g. find a building that is reg-tagged, rather than just having electrical violation. too many or unknown issues.

Somebody wanting to sue for you backing out of a bad deal or accusing you of selling them a property with defects like unknown termite damage).

----- there is too many unknowns , but as mentioned price,condition and value is the primary factors for a non-sale

But the unknown is where you are in the market cycle.

There could be something unknown that you nor the owner knows about. 

Honestly fear of the unknown and messing something up is why we are trying to avoid portfolio loans that and we do not know much about them. 

usually an eviction is done against "named tenant" and "any unknown occupants" or something similar. this gives you the right to evict anyone living in the property. otherwise, you can only evict the named tenants and anyone else living there is allowed to stay (and let the others back in).

It is an unknown and is set by what people do and because you cannot predict what people do you should only make decisions based off the numbers that you know and that are real.

Donald Rumsfeld, Ronald Reagan's Secretary of Defense, famously spoke about the "unknown unknowns" in a military situation.