The time to prepare your job application is now.
Why? Your musical career is just about to start. What on earth would you want a job for?
Obviously your sights are set on success. Some people will succeed and, if you can be among them, good luck to you.
However, many people who make a start in music find that even if they can make some money out of music, they don't make enough to call it the whole of their living. This applies to people who you would even consider quite successful.
And perhaps the world isn't yet ready for your music. It wasn't ready for the music of US composer Charles Ives (1874 - 1954). He pursued a career in insurance while he wrote music that, then, no-one wanted to hear. Now he is a national hero.
A career in sound engineering is however very possible, even if you don't get to be a musician. Well worth considering.
So, while all of that may be a long way off, it is worth starting to think about how you would go about applying for a job.
One thing you will need is a resume (CV). The other is a couple of references.
Your references are people who you will name on your job application form (not your resume) as people who will vouch for you and your suitability for employment. Your references should be people who are respected and will speak well of you.
It's never too soon to start thinking of who your references will be. You can always update them as your life moves on. Typically, at least one of your references could be a teacher at school or a tutor at college or university. You need to ask their permission. It's worth asking for open-ended permission, so you don't have to ask them again for each job application you make.
One problem might be is that people like this work with so many students, they can't remember them all - even the good ones. So even though you might have got straight A's in your exams, they can't think of anything to say about you.
So three pieces of advice about references...
Great home recording starts with a great home recording studio. It doesn't need to be expensive if you know how to select the right equipment for your needs.