You're fortunate to live in an era where conventional employment is not a necessity, especially for young people. Money may be required for all financial efforts. If not money then the willingness to invest a lot of time.
We don't know what mental issues may have, but if they happen to be ones of anti-social nature or general depression that keeps you isolated then you may find a certain degree of benefits from having a condition that removes motivation, or at least motivation to go out into the world. Here's why:
I make a very healthy income on the side that would be perfect for someone your age. I'll give a realistic number of $1,000 - $2,000 a month (and yeah, it actually involves stuffing envelopes from home but not in the way those ads promise). I make stuff and I sell it online. I make anything I feel would be a funny gift for someone, then post it on ebay and etsy, and amazon in some cases. A listing costs 20 cents, give or take, so like I said, you would need some money to start. And not all items listed sell.
I started with pillow covers. I bought material from a local sewing store, and made simple slip on covers. They sold at a profit of some $8 a piece. I ventured to other kinds of pillows. Some of which sell for over $100 a piece. Without divulging exactly what I sell now and thus running myself out of business, it suffices to say that I diversified my products simply by wondering what I wanted and looking them up to see if others sell them, how much, what they cost to make, etc. I now have over 400 items and generate between $40 to $100 a day just passively making things for about an hour a day, stuffing them in envelopes, and sending them in the mail. For $1,000 a month or so, it is very comfortable. It is easy work you can do while watching TV. Anyone can do it if only you have the motivation to spend several hours searching on ebay and etsy for things you think are neat and figuring out how to be the one selling the item and not the one buying them.
I freely suggest you make pillow covers simply because I proved the concept already and know it will sell. Plus, I don't sell sewn items anymore. A reasonable sewing machine can cost about $150. I have a fancy $1k one that is trash compared to my brutal janome machine that was less than $100. Just to give an idea about initial start up costs. You're not in a position to save, but you may be in a position to ask your family to support your efforts. I can't speak on how to set this all up. Only that I did it and it makes enough for someone your age to be effectively rich (relative to your needs).
Now, as time went on, my products changed. I always sought smaller, flatter, lighter. That way shipping costs are low, envelopes are cheaper than boxes, etc. Your best products are the ones that cost you the least in money and time to make, and can fit in a small envelope. Look at uline.com for shipping materials. A padded envelope is $3 at walgreens but 30 cents when you buy a box of 100 from uline. So keep all that in mind.
All sounds good, right? Well, it's useless if you don't know what to sell or how to make things. The bottom line is that everyone, and I mean EVERYONE has the skill to make something. Kids have those little bracelet making kits. Guess what, beaded bracelets sell on etsy all day long. Many of those sellers have sales in the hundreds of thousands. You can put beads on a string, yes you can. How about those bottle cap earrings? Or bottle cap tie clips? Point being, there's a market for almost everything. A little time and effort will show you what you like doing and what is realistic. I've been at this for about 8 years now and I promise you everything I have tried to sell will sell eventually. Diversify your products to appeal to many different types of people and you too can build up a healthy revenue stream that will always ensure you have a little something even if you're between jobs.
Now, for the juice of it, assuming you do this to some degree of success. As you grow older you should consider the normal path as like an insurance policy. Have a normal job to get by, to pay bills, etc. Have this side income as "play money" and by that I don't mean buy a fancy car. I mean use this money to invest in a variety of things that build your passive income and general future. Mutual funds, bonds, etc. All safe. Or more equipment to diversify your products even further and build the passive income. I do both now. And try not to tell people what you do because they may do it also and do it better and run you out of business. I abstract it the same way I am here. I sell online. You can too.
The one gem I will give you from all of this is that I am moving into digital products. Thus, removing nearly the entire cost of materials and the whole shipping process as well. Eventually I intend to build up a portfolio of several thousand digital items that trickle in a passive income of some $2k a month. It is looking very possible.
You can try to message me directly if you want more details.