Hiring guide is completely up to the trekkers. However if are travelling Nepal for the first time then you might need some help. You can find plenty of guide but picking guide from trekking companies is safer. A guide can charge up to 25 to three USD a day. They can tell you more about the trek and help you in case of any problem. A guide can act as a mediator if you want to communicate with the local people. An experience guide will also have basic medication in case of emergency. Furthermore, if you want to hire a porter then you can hire them from Pokhara easily.