How to start a business from nothing?

It would depend on the product or trade they had. In most cases it's a good idea to start online, because this can be done at low or no cost. Basically you need to find a platform to sell your stuff, and a way to advertise it. You can advertise among friends, by mentioning it on social media. You can also put your product on an auction site or on a crafts site that creates a shop complete with a shopping cart and "about me" page. You can just take pictures of your product with your phone and upload it directly, it's very easy. Sometimes these websites don't even charge upfront fees, but only charge if you sell something.