I only fly LPR, so this answer only applies to LPR rockets
Define “ready”. If you mean flyable condition but otherwise not prepped for flight, about 8 or so.
If you mean with engine, igniter, recovery wadding, and folded parachute all installed and ready to slide down the launch rod, then the answer is zero.
I fear an accident if I keep an engine and igniter installed in a rocket.
I install the engine and the igniter the morning of the launch day. At the launch site, I put recovery wadding into the bird, powder the parachute, and then carefully put the shock cord and parachute in.
I like to keep a plastic parachute unfolded and uninstalled until right before launch to prevent the dreaded “para-wad” phenomenon.