I'd say it's ready to send to an agent or publisher for their consideration once all of the spelling, grammar, and continuity issues (e.g., calling a character "Ramirez" on one page, and "Rodriguez" on the next) are resolved, and the story you wanted to tell is complete with a beginning, middle, and end. Anything past that point is problems with the story, characters, facts, pacing, or structure that will require rewriting to correct.