10% for maintanence

[Samir Shahani]

I am always puzzled why people allot 10% of rent for maintenance... 

I've talked to so many people and read so many posts of situations where the allotment is 10% regardless , eg.

Imagine a situation where the rent is $850/mo and the person allots $85 for maintanence.  In the same world (maybe a different city or maybe a slightly nicer part of town), another person is putting up a similar place in terms of age, size, condition, etc for $1600/mo and uses $160 as the allotment.

This is quite a different amount of money for two properties that may require similar maintenance costs.

I do it quite differently on my properties and am always looking to understand everyones point of view ... 

Can those who use this 'rule of thumb' stir up some conversation and defend your rationale?!