travelled solo back in June this year for 2 weeks... should have done 3 for an ideal duration.
did the almost standard tehran > isfahan > shiraz > yazd > kashan > tehran. flew in and out with etihad with stopovers.
used CS for meetups in tehran, stayed in CSer's house in isfahan, stay in a local's house in tehran at the end after randomly chatting with him in shiraz/persepolis.
standard hostel bed rates in bigger cities usually around 15USD/night
they quite hospitable and curious about foreigners so be prepared to be approached by a lot of random people trying to speak to you in broken english/sign language
enjoy the trip!