Who does not use the 50% rule?

[Levi Gale]

Hello,
Who here does not follow the 50% rule when analyzing/purchasing a property for long term hold? There are a few reasons I can see someone not using it i.e. they are relying on appreciation (not my cup of tea), they look forward to equity build up and loan payoff, or maybe they are seasoned investors that know their maintenance and management keeps at a certain percentage.

I am in Arizona a market that dropped significantly since the boom, and I'm starting to think some investors are buying at FMV simply because they expect appreciation. I don't view it as a wise investment, but hell I could be wrong. I view this as the type of speculation that had everybody and their grandmother buying during the boom. Am I wrong here?