Depending on where you live, what kind of music you like making, and how much time you plan on putting into it, it certainly is possible. My advice doesn't come from experience with AudioJungle necessarily, but freelancing/self-employment is sort of similar no matter what you do, so my personal experience is this:
Whenever someone decides to do something like this (start a business or get serious about making money from your hobby/passion) and start relying on passive income, they should realize a few things. The first is, for at least a little while, you probably won't make what you'd make at even a minimum wage job. In other words, you won't be working a set amount of hours and getting a steady paycheck in return. Instead, it will seem like you are making much less money, but in reality you will probably end up making just as much or more as you would from a steady job, it's just that your income is now being stretched over an extended period of time because all of your sales will not come at once. This might seem like a bad thing, but if you think about it it's actually a good thing, because each piece of music you sell has the potential to keep generating money for you indefinitely. It's like an investment, whereas with a typical job the only thing you ever get back is a paycheck. A single track might make you a few hundred dollars, but it could take months or years to sell that much. It could take days or hours too, you just never know - which leads me to my next point.
It's a game of averages. Just like any business, not all of your products/tracks will be hits or even slight successes. This is probably painfully obvious to most authors, but to again compare this to being employed, with a regular job you will always get paid for your time, even for doing nothing, whereas in a business like this you might never get paid for your time, but hopefully you can make it up with other tracks, or you make it up in the long run.
Be prepared to do promotion and marketing. I don't know if you can really have a good amount of success here (or anywhere else) without spending some time on promotion or marketing, because otherwise how would people know about your product/music? You can't just rely on AudioJungle searches, you have to push yourself and your product out there. Free or paid promotion, whatever works for you, but if someone is serious they really can't be afraid of spending money on promotion and advertising. After awhile hopefully you'll achieve some kind of presence and won't have to do this as much, but it never hurts.
I'd definitely try it, if it's really want you want to do. I would probably save up some money first if at all possible, so you can take a year off (or whatever amount of time) and really focus on doing this seriously. I think if you are able to dedicate that much time to it, you'll either start to see how it's possible or figure out it's not for you. Either way, after a year, at the very worst you'll have a passive source of income that is making you money on top of whatever job you decide to take. Hell, I don't write the kind of music that sells well here, and I definitely don't live in a cheap enough country, but even I think it would still be possible to get close to making a living if all I did for a year was write stock music. Personally I wouldn't put all my eggs in one basket (with AudioJungle), but that's just me. It's amazing what you can accomplish when you dedicate your time towards doing what you want as opposed to throwing it away at a job you don't really like. Most jobs don't go anywhere, not any of the ones I ever had anyway. At least with something like this you are taking your future into your own hands.
Oh, and at least some friends and family will tell you that you can't until you start finding some success to throw back in their faces but I think mostly they are either jealous they have to keep working their slave-jobs, or otherwise they really don't understand that it's possible to make money being self employed/freelancing, but it definitely is.