Summarize this article in one sentence.
When you go to work as an independent middleman, you'll be establishing your own business. Start-up costs are fairly low for this type of work and you can get started quickly, but you still need to treat your work as a business both professionally and legally.  On a basic level, dedicate the basic space and supplies needed to do business. You should have a separate business phone line, a fax machine, and a business e-mail address. If possible, dedicate a separate computer and corner of the house for business purposes alone. On a more advanced level, familiarize yourself with the legal side of establishing a business. Set yourself up as a business entity. Research any restrictions involved on how the product/service you want to provide can be traded. Make sure that you know how to file your taxes and do so accurately when the time comes. Observe the marketplace and look for a niche you can slip into. The biggest need will be in an area where the supply and demand structure is sluggish or does not otherwise satisfy the consumers and suppliers.  Services or specialty products are usually easier industries to break into as a new middleman. Generic products that are readily available are often purchased direct from manufacturers, and convincing a retailer to change can be nearly impossible if the system it currently uses works well. Determine who the consumers of your chosen product or service are. Depending on the nature of your intended business, these consumers might include both local and non-local buyers.  When you're dealing with a product, this usually means researching retailers who would be interested in selling that product. Research local retailers by looking in the phone book or searching online. Research non-local retailers by looking through online databases of retailers. Focus your search on small and medium businesses instead of major brands. When you're dealing with a service, you may need to rely on more traditional advertising to find individual consumers and business entities in need of that service. Start with the parties you first observed the need through—oftentimes, this will be someone you know personally or a local business. Work through that source to find other potential buyers who face similar issues. After making a list of potential buyers, give them a phone call. Find out what they need and what you can do to encourage them to buy through you.  You can send an e-mail to touch base with your potential buyers, but contacting consumers by phone can often leave a more professional impression, especially when you're dealing with businesses instead of individuals. When you contact retailers, try to speak directly with the purchasing manager. Ask that individual if he or she would be interested in seeing a wholesale price list. If the answer is "yes," promise to get that list to the retailer within a few business days. Find as many potential suppliers for your chosen product or service as possible. Do your research on each one and narrow down the possibilities to the top ten.  When dealing with products, you need to search for manufacturers. Unless your focus is strictly on a local product, this may mean searching for international manufacturers. When dealing with services, the suppliers will usually be local. Contact your potential suppliers and ask them to provide price quotes on a certain quantity of product or quality of service. After gathering these quotes, compare them and determine which suppliers offer the best value. Take into consideration the entire value of the quote. The supplier with the lowest quote may not be the best one if the product it supplies is dramatically inferior to the product another supplier offers. The same can be said for suppliers of services. You will earn money being a middleman by earning a certain commission from each sale you make. While the exact amount can vary, commissions of 10 to 15 percent are common for many industries. Note that suppliers who already work with other middlemen may have a set commission fee they allow middlemen to charge. Determine if this is an issue before you try setting your own commission. Make contact with your list of potential buyers again. Deliver the final cost of the product or service with you cut included in it. Factor other fees you'll need to worry about, like taxes and shipping costs, when providing the final cost to your potential consumers.

Summary:
Set up your own business. Identify a need. Research potential buyers. Get in touch. Research potential suppliers. Ask for quotes. Add your cut to the cost. Pass the information onto the buyers.