1) Income from your creativity

If you are good at something, never do it for free.
If you have a hobby like painting, quilling, photography etc., can make it earn for you.

Initially, the payment may be less, but, in the long run, it can be solid stream to earn money. You can also start a summer camp for kids and extend the same to a regular camp.

2) Income from Real estate

One can generate income from a vacant land as well, which you may own. Now in metros, there is a trend for parking vehicles in a parking area due to a shortage of space or no parking availability.

The piece of land can be made as a parking area and one can charge a fee on hourly basis or as is required.
One can also rent out additional rooms to generate income.

3) Investing in fixed instruments

Instead of having money in a savings account, it is better to invest the same in income generating instruments depending on the risk such as Post office MIS, tax-free bonds etc.

4) Monthly Income plans

Monthly income plans from mutual funds provide you with regular income without guarantee on returns. If you are ready to take a slight risk, it can give better returns.

5) Online Surveys

Enroll yourself for online surveys which pay you an amount for doing a survey. There are survey websites that permit you to do so. All you need to do is answer some question and get paid for it.

6) Other ideas

One can also consider creating a blog, providing contents for established websites, freelancing business. Say for example, if you have good knowledge on any topic and expertise and a certificate in that can be used to make money by giving seminars, and can be a guest lecture in school, college or any institutions.