Having multiple streams of income is a good thing because if one income stream suddenly gets cut off then you always have another income stream to fall back too so you don't run out of money.
Some good ways of creating multiple income streams are, starting a blog, promoting affiliate products, do online work such as through fiverr or other websites.
You could also get a second job or just a side job or buy homes and create income by renting them out to people who need a home.
People will always need a home and cannot or do not always want to buy a home so they would rent a home instead.
You could also start an ebay store and sell on ebay or make youtube videos and monetize your youtube channel so that when people watch your videos and ads then you make money doing so.
If you create good interesting videos and get a lot of views and subscribers then you could make more than your current job.