For multi-unit deals, how do you estimate CapEx and maintenance?

[Tammy Richards]

I love analyzing multi-units, and have a couple of different spreadsheets from different sources. I'm wondering how folks estimate CapEx, maintenance/repairs, and turnover costs?

My current spreadsheets use 10% of gross annual rent for maintenance/repairs and 5% gross annual rent for CapEx. That's fine, but it seems like it would overestimate costs for a high rent/higher # units property, and underestimate costs for duplexes and lower rents coming in...

Do people use other methods than this?  Maybe % of purchase price (though that would mean low estimates for killer deals, and higher estimates for hot market properties)?