There are language institutes who need native English teachers. They also need French and German teachers too. Most of the Iranian teachers speak English VERY badly. I've talked to several English teachers and one of them asks me very basic questions over Whatsapp almost every day. Also, the books they use are based on American culture and there are things in the books that they can't understand. Yesterday, he asked me what a King size mattress is. Apparently, he can't just google it.
Qom is the cheapest city in Iran from what I've heard. You can live on about $300 a month here easily. Bring dollars and you can live comfortably because most jobs in Iran aren't high paying. Also, it's hard for foreigners to find jobs besides teaching English.