Formulas for flipping?

[Brandon Miles]

Hello, I am not a flipper and don't pretend to be. 

I was wondering though those that do, and have experience with it if there are any formulas you may use?  or a rule of thumb on how much money needs to be injected into a home to bring an outdated home to sparkling brand new (this wouldn't include foundation or structural issues)?

I recently did a remodel on a condo to turn it into an airbnb. Since I am not handy nor do I deal in major quantity of flips I would think my costs on doing work has to be much higher than you flippers out there. I remodled a small spot (650 sq ft), and took remodeling costs divided by total purchase price of the place and came up with 13%. Now I am not sure if this is a great number or not. I would love to hear some feedback from you flippers out there. 

I did the work in Scottsdale, Arizona. I'm sure every market has different labor and material costs so this won't be comparing apples to apples, but would greatly appreciate any feedback. Really appreciate it and thanks in advance for reading and taking time to answer my questions.