It can be started in low budget. Platforms like Hostinger provide free domain
YouTube channel is also a very good idea among the top online business ideas.
From digital art to big manufacturing products, you can also sell online.
If you buy any product online, then you get some commission for it.
If you are a writer / author then you can write your eBook and sell it online.
You can sell your photos online by clicking photos
You can create tutorials online. In whatever field you have knowledge
Website designing is a very reliable job today.
SEO Consultant becomes a bit higher level work. This is not a small job.
If you want to do part-time job online, then you can work as a freelancer.
If you have command over computer programming languages then you can develop mobile applications.