STR operating expenses

[Kyle Smith]

I have a spreadsheet I've developed for my STR and have been using 20-28% for a management company to manage the cleaning, booking, and maintenance. However, after doing some reading here I am leaning on doing the booking myself through VRBO and managing it myself. I'm building a 3br pool cabin, so I know there will be an added expense for the pool, but I'm curious if there is an average percentage number I could plug into my spreadsheet to represent the cleaning, maintenance, etc. if I manage it myself? Is it 5%, 10%, etc of my gross income for the year if I manage it myself? I would love to know about your experience. Thanks in advance.