for starting a exchange the basic thing what you need is a big budget in your pocket.  Because you are creating an exchange you need to hire programmers.  ok may be your friend can do that. But it's your duty to cross check the codes of the script or test the script with the help of another programmer because you are going to handle others money. you will also need money for advertising your site like signature campaign etc to attract visitors in your site. so if you dont have enough money please dont step into this business.