Basically you're looking for something to be the next BTC or ETH. Not gonna happen with your short time frame.
If coin like DASH pumped to more than half a billion marketcap, an initial investment of 20K at the beginning of DASH would have made OP lots of money.
https://coinmarketcap.com/currencies/dash/Price of dash in Jan 2016: 0.0075 aprox, thats 3.25 dollars at current price: 6153.85 DASH = 472.95 BTC = 488,700 USD
Thats almost half a million for holding a coin for 1 year. Notice how it could have been more, since January 2016 was not the beginning of DASH, DASH was cheaper back then in 2014/2015.
With ETH, it could have been more a couple millions (too lazy to calculate it, look it up yourself)
So we must find a coin that's:
1) Flat
2) It's not complete dogshit and has active developers so it doesn't get delisted
3) Take a big bet and hold
Opportunities are shrinking since most horses have been beaten.
The "smart contracts" horse has been beaten by ETH
The "anonymous coin" horse has been beaten by XMR
and so on.
Even tho sometimes additional coins emerge in the same niche that can deliver "fuck you" type of money
Take PIVX for example.
3 figure satoshis for a coin for 1+ year
So let's say you bought at 500 sats on average during a period of time to not pump the market, 20k worth of PIVX
500 sats per PIVX x 19.35 BTC = 3870000 PIVX = 2,997,222 USD
that's almost 3 million dollars
Not sure if i've fucked up in the calculations (I suck at math) but yeah, it's a lot of money
Notice how PIVX was still around 1500 sats during January 2017, so he would have made 1+ million in less than 3 months of holding.
The problem is, who the fuck would have spent 20k on PIVX? so there.
I understand your position tho, I would rather die than be poor for the rest of my life. Not being rich is like being busted in the balls daily. Let's just hope the stars align. At least now I got enough BTC to make big bets. Back in the day I didn't had any to invest.
PS: Some say PIVX may hit 10 dollars. LTC also hyped up in the fork BTC crisis due segwit and whatnot, the last ATH is a psychological aspiration in market participants once the pump begins. Those are 2 reasonable bets I guess, but the higher you get in the more insane of a bet it becomes so good luck.