Question about calculating a % of rental income to set aside every month

[Steve Balinski]

Hello everyone.  I have a rental calculator that is very detailed, been using it for quite a while but it is different than most rental calculators out there because it asks for a dollar amount for each month/year to set aside vs a % like most calculators use.  

That being said, for CapEx/Yard Maintenance/Repairs/Overall Maintenance is there a general % that all comes out to? I'd like to modify my calculator to just enter a % of rental income to set aside for all. I've seen other calculators and articles stating 50%, but the 50% includes insurance/taxes etc, I've already got a different section for that.

I've seen 8-10% for maintenance, 8-10% for CapEx, 8-10% for repairs. Is 30% a good number (obviously this can change depending on the age/condition). I have a 4 unit property generating 4200/month in rent. 10% just for maintenance is $5k a year which seems REALLY high....that'd mean I put away 15K/yr for maintenance, repairs, CapEx.....seems unreasonably high, no?