The forums are rife with young people interested in pursuing a career in audio. There are many ways to get into the business and many places to end up. There's the school route and the learn on the job route. The answers are as numerous as the questions. But this isn't a post about how to do it. This is a post about what it's like to do it.
First off, you need to love what you are doing. Only the best of the best ever get rich. Realistically you need to be above the 70th percentile to make any kind of living from just doing audio. There are plenty of rewarding pursuits at lower income levels, but if you're going to make your bread solely doing audio stuff then that's how good you need to be. So it had better be about the love. I sweat it out as a weekend warrior for over a decade before I got there. I happily swung a hammer all week and then humped my gear into bars and halls to spend the weekend turning knobs and rocking out. It wasn't for the measly couple hundred bucks that I stayed out till five in the morning.
Secondly, the people around you need to understand that this isn't something you do, it's who you are. Any significant other that you plan on having be truly significant will have to get this about you or things will not end well. A spouse that thinks you're going to give up late nights finishing mixes or loading out gear to sit home and watch Netflix is going to be sorely disappointed.
That said, they should understand and be grateful that your day job is fulfilling. Lots of people slave away at jobs they hate. Even if you're not making great money, job satisfaction makes ramen noodles and cheap furniture seem a lot better. If your audio pursuits are of the weekend warrior type, your people should be grateful that you're not spending thousands on bass fishing equipment or season tickets. You're contributing to society and bring in money.
Know that you're going to miss out on special events. First steps. First words. Family reunions. Birthdays. Anniversaries. I miss those kinds of things all the time. But my family has adapted. There's not really any such thing as special events for us. We have Christmas the day after. We have birthday parties a week earlier. We have super fun together on Monday mornings because that's when Dad is home. It's no big deal and I for one find it much more satisfying than being tied up in a nine to five occupation.
You're also likely to have to work on a lot of stuff that you don't like. I'm a big metal head and yet I hardly ever get to mix metal shows. Instead I find myself booked year after year at the local accordion festival, or mixing musical theatre, or making records for the local awful emo bands in my garage. You have to be willing to find the good in a lot of stuff that's not up your alley so that you're not too bitter to miss the enjoyment when you finally get a good one.
Don't think of it as selling your soul or selling out though. I have a good friend that did an extended world tour with a famous female pop star. Most people would rather remove their own appendix with a soup spoon but he lived through it and now doesn't technically have to work for the next three years if he doesn't want to. Pretty sweet to stay home with your cute wife and baby and only take the occasional gig that interests you.
You will suffer for your art. Those close to you will also suffer for your art. You will hurt your back, either from hunching over a DAW or from pushing boxes on and off trucks. You will struggle financially. You will deal with hateful, diva performers and get screwed by shady promoters. You will not sleep well. You will not eat well. You will find yourself doubting your entire life at five in the morning. But if you really love it. You'll go after it anyway because none of that crap matters. You are the Brethren of the Knob and Fader.