@Ross Dillingham Those are industry standard tests for quickly evaluating a deal.
Rule of 2: The 2% rule says that for a rental property investment to be “good”, the monthly rent should be equal to or higher than 2% of the purchase price. I actually had a flub in my calc - change it to monthly rental income / purchase price. I don't really pay attention to this one as its not realistic for my market. I generally shoot for over 1%.
50% Rule: another gauge to quickly analyze a deal. Most investors find that their operating expense historically net out to 50% of revenues or rental income. There is a lot that makes up op expenses and its probably the trickiest part of analyzing a deal. But to quickly apply while analyzing: Total rental income - (total rental income *.5) = NOI. You can then apply your debt servicing to arrive at cash flow.
There is no 40% rule, I made it up as I feel 40% is a more accurate gauge for me. Expense as a % on income is just showing how close I am to 40% or 50% i am in my operating expense assumptions.