0%.
I think $1.5m ARR is too early for an experienced COO in 95 cases out of 100 — unless it’s a total rocketship and you plan to be at $10m+ ARR within 12 months.
At $1.5m ARR you should still be the COO. You should find, hire, and manage the VPs of Sales, Marketing, Customer Success, Product and Engineering and even Finance yourself.
At $8m, $10m, the operational side of the business may be so complex a COO makes sense.
Today, the main operational challenge you have an Initial Traction is hiring great function VPs.
Go find them.
And stop wasting time on an idea of a magical “COO” too early.