Thanks to modern DAWs, you can compose, edit and produce your music all by your self. It takes some know how and practice but it’s not prohibitively difficult, nor expensive.
Now many will tell you that "do it your self" production isn't good enough. That no one will like your tune if it never gets passed leveling stage. That you MUST get professionals to process/mix/master your tunes.
I say nay.
Don’t let anyone convince you that your art isn’t good enough without the “professional” treatment. If you are competent enough to do good leveling on your tune, you are already at 90% completion in the music making process. If your music isn’t good enough by then, it’s not good music to begin with and you do not benefit from pretending it is.
Before I continue I should explain some terms: "Tracks" often refers to audio channel assigned to individual elements or instruments. "Leveling" is the act of adjusting the sonic character and volume of each instrument or element in the tune, so they all fit well with each other. This is usually done by applying the appropriate production tools to each individual track such as: compression, expansion, equalization, limiting, automation, effects, gating, noise reduction, phase correction, ect. "Mains" refers to the stereo channel that all tracks flow into. "Monitoring" refers to properly designed and adjusted speakers that do not color the sound so they don't mislead your mixing decisions. "Room treatment" is the application of properly calculated acoustic materials so the room doesn't color your sound/mislead your ear. "Headroom" is simply how much level you have left before a sound maxes the meters and begins to clip (clipping bad).
Mixing is fine tuning the sonic character/color/balance of the tune. Mastering is polish. Nothing less but nothing more. I rarely see people ask: Will the mixing/mastering steps change the melody? The beat? The lyrics? The arrangement? If you have done a good job leveling your tracks, the answer is most definitely no. It’s just polish. It might surprise a lot of people but some of the most memorable pieces of music in our lives were not “properly mixed and mastered” by today's standards.
Now will professional polish make your tune sound better? Sure. It gives a piece of music that mirror finish. Before you spend a ton of money on professionals though, consider this: Most listeners aren't audio engineers. They neither care nor know what kind of processing has been done to your music. They only care if the music tickles their fancy. If it's good music to begin with, it will. A large part of what you are buying with professional processing is a stamp of approval from people and an industry that DOESN’T care about you, DIDN’T compose your tunes, AREN’T fans of your music and likely WONT ever purchase or support your art in general.
Expressing yourself deeply and honestly. Finding and connecting with your audience. Gaining exposure and revenue. THESE are the things that matter the most. If you are going to pay a professional to do something for your music, you'd be much better served hiring a promoter to get yourself exposure. Buzz is WAY more important than whether or not your tune is super polished.
But what about being loud? Streaming services standardize the playback volume of music. Spotify for instance, runs at -14iLUFs. So all you need to do is make your tunes "loud enough" and that's not hard to do. You don't have to mix to -4iLUFs or something ridiculous if you can't or don't want to.
If you are disappointed with the overall sound or loudness of you tune, take the time to master proper leveling techniques and don't rule out the power of proper plugins for the job. If you take the time to apply the right tools to each track and use a few critical plugins on the mains, you might be surprised just how good your tune can sound all by your self. Some of the most powerful types of tools I've found did NOT come with my DAW.
Here are some of my goto tools:
https://www.meldaproduction.com/MLimiterMB (though it acts more like a compressor it's great for controlling an overly bassy mix without trashing quality)
https://www.waves.com/plugins/l2-ultramaximizer#how-to-limit-mixes-masters-peak-limiters (indispensable tool for bringing your mix up to competitive loudness)
https://www.tokyodawn.net/tdr-nova/ (fantastic for individual tracks that have nagging EQ problems)
https://www.meldaproduction.com/MSaturator (for adding presence/loudness to wimpy sounds without eating headroom)
https://babyaud.io/smooth-operator-plugin (great for adding just a touch of expansion/compression to a mix)
https://www.meldaproduction.com/MLoudnessAnalyzer (indispensable tool for analyzing iLUFs loudness on the mains)
Last and not least is a fast response real time spectrum analyzer. Like this: https://www.meldaproduction.com/MEqualizer I don't own that last one because logic has one already built into it's channel EQ. It is however THE MOST USEFUL TOOL YOU CAN HAVE. Because no matter what you can or can't hear, you can ALWAYS SEE what's going on.
The biggest advantage to having your music professionally mixed and mastered is professionals have proper monitoring in a properly treated room (a very expensive thing to do). Not having this is the biggest oversight and weakness of DIY at home producers. It doesn't have to have such a huge impact on your music though. If you learn to use a real time spectrum analyzer, you can SEE what a pleasing sound profile looks like. You can SEE the major "problems" in your mix. You can see how effective your solutions are. This is a great way to get good leveling and even a little mixing done by yourself. You can use it on individual tracks/instruments as well! A lot of professionals will bad mouth "mixing by eye" but it is a fast and most importantly an at home ACCESSIBLE technique to get a tune well over the 90% mark.
I got most of my plugins and info for a fraction of the price I would have paid a mix/master engineer for processing just one album. : )