TBH you can start flipping at any bank. It should always bring in some extra gp. I started around 7M cuz that's when I learned how to flip. Do things like D hatchets, barrows items, sol's, whips, etc. This caan get your stack up enough to the point I'm at where you can flip ags', stead's, and arcanes. It takes some practice but I think you're far past ready to begin. Good luck:)