50% rule in New Brunswick (Canada)?

[Hannah Westner]

Hello, BP newbie here.  

I was watching this video by Brandon recently and found the method interesting for helping to identify properties that might be worth a second look (https://www.biggerpockets.com/renewsblog/2013/04/09/how-to-buy-a-small-multifamily-property/).  

However, he talks about a "50% rule" meaning that you can roughly estimate that 50% of rental income will go to expenses and the remainder is left to pay the mortgage and generate cash flow. 

For those of you investing in New Brunswick (Canada, not New Jersey) do any of you find this useful for your initial analyses?  In New Brunswick, where we pay double property tax for non-owner-occupied properties, is the 50% rule a good estimate?  

(Recognizing, of course, that it's just a rule of thumb!) 

Thanks