As stated, there really isn't just one standard. I have created a checklist for my softball team but even it is subject to change. I was asked by a parent this past weekend when I was sending it home as I did last year. He lost the last copy. Baseball is somewhat different in that in softball, they get them early. By the time BB was a sophomore, she was taking unofficial visits. Heck, at her "dream school" then, she was on one of those unofficial visits when that team's new uniforms came in. So, the coach asked her to try one one and we took a photo.
Here is what I have deduced. You can get mid D-I interest junior year and they have some scholarship money available. KEEP IN MIND THAT NO ONE IS GETTING A FULL RIDE unless you are a stud pitcher. Maybe, once in a while, a stud catcher. So, everyone gets partial money but it isn't much. I believe in D-I that they have to offer 25% to anyone on scholarship but might have changed. D-II don't have the academic requirements of D-Is. D-IIIs are a mix but you do need to have the grades. NAIA and JUCOs, in my experience, will take players pretty late in the process.
Granny said Sonny stick to your guns if you believe in something no matter what. Because it's better to be hated for who you are than to be loved for who you're not.