@Jonathan Gregori
Multi-family's (typically 5+ units) are valued based on their income. The method you bring up seems to be working around this formula:
Cap Rate = NOI/Purchase price
For first run analysis you can assume that NOI is roughly 50% of rental income (50% rule).
The rules you present have us multiply the gross rents by 12 to get yearly gross income. The yearly gross income is then multiplied by 7 to get a target price (+/- adjustment)
So:
Purchase Price = Monthly Rent * 12 * 7 = Monthly Rent * 84
NOI = Monthly Rent * 12 / 2 = Montly Rent * 6 (Standard assumption based on 50% rule)
Cap Rate = (Monlthy Rent * 6) / (Monthly Rent * 84) = 6/84 = .07142 = 7.14%
Is that the Cap Rate you desire? Is it the current Cap Rate for the market the property is located in and the class of the property?
There are two assumptions built into the calculation as I've broken it out. The first is that expenses are 50% of Gross rents. The second is that the Cap Rate you are targeting is 7.14% When using guidelines it's sometimes good to know the assumptions built in.
Bottom Line, these are all tools for analysis, but do no good if you don't know what you are looking for. You may be better served by developing criteria of what you want and then you can create your own guidelines to evaluate properties and determine what is a good buy or not.
Below is a table. Multiply Monthly rents by the number next to the cap rate to determine an approximate purchase price based on a NOI of 50% expenses:
For a Cap Rate of 7% take Monthly Rent and multiply X 86
For a Cap Rate of 5% take Monthly Rent and multiply X 120