There are many people that make money buying and selling things online and there are different ways of doing this. You can buy online or offline and then sell online or offline but you need to make sure that you can buy the items cheaper than you can sell them for so that you make a profit. Research first to find out how much things cost to buy and what you can sell them for.
There are lots of places where you can buy things online. However, if you are looking to buy cheap items then you need to go to places which are less well known. It is likely that you will need to buy in bulk if you want lower prices and so you will be taking more of a risk. However, it will be worth it if you can sell the items and make a profit. You can look at various places to find them and depending on what sort of thing you are looking for you should be able to find some at good prices. There are some online wholesalers, for example, which may have the sorts of things that you need. You may find that you need to be a member or prove you are a business to be able to shop there, but you should be able to sort that out fairly easily. You may find that some auction sites will have wholesale sections where you can buy items cheaply in bulk. Some of these could be foreign, so you may feel that you need to be cautious, but apart form taking longer to arrive, there is normally no need to worry. Look at reviews of the company before you buy and you will get an idea of what they will be like to deal with.
There are many ways to sell online. You can go through your own website, auction sites or retail websites. With your own site, you will not need to pay commission on sales, like on auction or retail websites, but you will have to pay for your own marketing, unlike with a larger site that is already well known. Some people will try selling across a selection of platforms to figure out which works the best for them. Often customers will trust a well-known site more even if the same products are for sale on it than individual websites as they know that they will be able to return them if there are any problems or easily get in touch with the customer services. What you decide to do may depend on the items that you are selling and what your competitors are doing. It is very important though to make sure that you charge the right amount of money for postage and make sure that you charge enough for the item to cover the selling fees as well as the price of the item plus a profit margin. It can be easy to miscalculate and sell things too cheaply and end up making a loss.