Yikes - Who told you that?
Can you give us a little more information about the types of shirts you are trying to decorate? Are the light colored or dark colored? Are they 100% Cotton, a blend of Polyester? Also do you have a heat press or are you planning to just use a home iron to transfer the images?
There are several great heat transfer papers out there, so let me know the above answers and I'd be more than happy to point you in the right direction.