Does the 70% rule work everywhere?

[Mark Russell]

I’m in Fredericksburg tx. This is a tourist town with 2million + visitors annually. The real estate here is booming. It has been for years. Everyone here knows there house values appreciate at a much higher rate than most areas in Texas and the u.s.  Austin is even crazier. That said.. is it sensible or not to use 75% as opposed to 70% in an area like this? 

[Mark Russell]

@Michael Lam that makes perfect sense. Now this concept is not so vague and foggy to me. Thanks!