Domain trading is considered as one of the high profit businesses, you can do online. However, unlike other earning methods online, you will have to make some investment. Investment is to buy domains.
You need to get knowledge and be an expert before stepping into this business. You can purchase domains from GoDaddy or other domain registrar in less than $10 and later sell it to the person who need it, in high profit like 50$ or 100$ or even more.
You need to develop skills of identifying good domains that are not bought by anyone yet and which could have huge demand in the future. When people or companies don’t find the domain of their choice, they contact the domain owner for the deal and the current domain owner then decides about the price.
Domains can also be sold on auction.