Is it needed, how do you obtain one? I am new to the business and have a few customers that would like their yard fertilized. Should I sub-contract another company or do it myself? I need to know more about times to apply what and what to apply. I have no problem making my own yard look great but if i happen to screw it up the only one to get mad is my wife (and neighbors if I really screw up). Thanks for the help, it is truely appreciated.