I'm an Australian planning to travel to Mashhad in late January. I'll be in Lebanon in November and Syria (Aleppo only except transit) from Dec-most of Jan. I've heard that visas only last 3 months from the date of issue. Given that I will be leaving Australia in late November, this is probably cutting it too fine.
Fill in the visa form on Iran visa , it takes about 10 working days to get your reference number and two working days to collect your visa at the embassy by direct referral or one working week by posting the docs to the embassy. You can pay the visa fee in cash in Iran.
Check the cheapest Iran tours.