How do you make your own mmorpg for free

The short answer is you can't. The minimum cost is about $600, because you need server space, a web site, and Adobe Flash CS5.5, plus SmartfoxServer. Usually making a game on such a low budget causes the game to become a morpg not a mmorpg though. A bigger, more experienced team of people would help much more than a single person. Although hiring a large team of people can cost a fair amount this can be paid for by pitching your idea to business men/women, and offering a % of your company to them (see dragons den/ sharks tank), if it is a smaller group then this may not be needed. Baring in mind that you need a CGI team, sound effects team, management team , programming team , theme tune/ area music team , concept artists etc this can cost millions, so i would recommend getting a job in a gaming type field and slowly get promotions and pay rises until you can start your own small company. start with a plot, maybe get some friends to help with your project, then start designing the concept, how it looks, scenes and maps.
If you are under 18 the chances are that you may never make your own mmorpg because by the time you are 18, the dream will be over, but never let go of the dream because some day it may be a reality.