Should your plans include collecting your visa for Iran in the Turkish City of Erzurum it is very easy to get very cheap accommodation while you are there.
If you get to Erzurum during daylight hours and make your way to the Iran Consulate, even if it is closed for the day, have a look out for a taxi driver that is parked up outside the consulate. He seems to ply his trade there.
I have seen him there everyday for the past week - yes I've been going to the consulate every day - even on the closed days. Because the consulate is visited by everyone with concerns for Iran I suppose the guy has his head screwed on. I have met Iranians there that have arrived in Turkey with no passport, he finds them a hotel. Those that have lost passports, those that need visas - everyone turns up everyday.
He found me a hotel for 10 YTL (Turkish Lira) a night. Nothing spectacular about it, but it was a private room with wc/shower. No food or drinks included, but what more do you expect for €5.00 (euros).
If you are not sure he is the right taxi driver wait a while and he will always return and park in the same place.
Hope this info is of help to some.