2% Rule vs. Rule of Two

[Justin Foster]

I'm reading a free book on REI from http://iloverealestate.tv/ in which the author talks about a rule she made up called the Rule of Two. In this, you divide the purchase price by 1,000 and multiple that by 2 in order to get the minimum weekly rent you should charge.

(Purchase price / 1,000) X 2 = Weekly Rent

In the 2% rule, we multiply purchase price by .02 to get the monthly rent that we should try to get close to.

So lets say a property has a purchase price of $200,000.

Rule of two gets us $400 weekly rent. Multiplied by 4.3 for the average weeks in a month, we get $1,720 monthly rent to use as a starting point.

2% rule of the same price shows us to get close to $2,000 monthly rent.

While these two results are close to each other, there's still a significant difference between them. Which one would be more useful to go off of? Or would it be useful to use both and go for a number in between the two?