Not sure what you mean by low capital but I'm just going to assume that it's less than $1000. 

So here are a few ideas for online businesses that can be started with less than $1000. 

1. Affiliate blog: Here's how it works. You pick a suitable niche, a domain name, and find some affiliate offers in that niche. The most common affiliate network is Amazon. It pays you a percentage of sales that are generated through your blog. There are thousands of other affiliate networks like Shareasale, Clickbank, CJ, etc. The network you choose depends upon your niche. 

To get started with an affiliate blog, it's very important to learn some SEO and SMM skills. It will take time but you will get there. 

2. Freelancing: You just need to set up a website where you can provide services such as (content writing, designing, animation, marketing, etc). Do some Facebook or Google ads to find clients and start earning. Alternatively, you can also offer these services on platforms like Fiverr, Upwork, Seoclerks, etc. Just sign up and start earning. You won't even have to buy a domain or set up a website to get started. However, there's a ton of competition so you must get creative to make your service stand out. 

3. Trading: I don't usually suggest this because this can be risky and you may end up losing your investment. Make sure to learn as much as you could before investing a cent. Also, don't get involved in options trading or any other type of trading that's similar to gambling. I'm only referring to crypto and stock trading.