Well if you have a job, make sure to invest some of the money, you get by it, at the end of the month in Bitcoin - like 5%-10% or something. I think this will be the most secure way, since you wont notice the money you are investing and you will always have some Bitcoin. Then just keep the Bitcoin and don't touch it - by a couple of years your investment may turn into "gold" 
The other thing that comes to my mind is to invest in some Proof of Stake alt coin that is promising - like for example Solarcoin, which is growing stronger and stronger everyday, and just let your wallet stake the amount and your coins will grow by a small amount everyday 
Actually not people have the capability to find job in related to age. So if you want to earn still enough to support your investment plan it is better if you are going to be open on considering applying on a signature campaign where you can have the opportunity to earn bitcoin. And when you earn you could actually used it as a form of capital on investments or in trading where you could possibly earn bitcoin and make a profit out of it. So the best thing to do to have a stable income is by continuing doing your part for you to earn. The other thing that comes to my mind is to invest in some Proof of Stake alt coin that is promising - like for example Solarcoin, which is growing stronger and stronger everyday, and just let your wallet stake the amount and your coins will grow by a small amount everyday