Board Thread:New on Terraria Wiki/@comment-24.147.239.114-20130606224720/@comment-14029319-20130731102726

Well, you need a house (8 wide, 5 high) for the merchant. The building also needs a light source, a table, (or crafting table) and a chair. There are a lot more items you can use instead of a table and chair but I find those the easiest to obtain. Look at Home for the specifics.