@CanuckExpat we had to store our RV once while out of the country and found a very affordable place way out East of Phoenix.
They were cheap for the first month only. So if you need more than a month, it makes sense to shop around and price out your specific time frame.
As a rule of thumb, the further East or far West you go from Phoenix proper, the better the pricing.
We used Cost Less Storage, 2519 W Houston Ave, Apache Junction, AZ 85120
https://www.storage-solutions.org/storage/arizona/storage-units-apache-junction/2519-W-Houston-Ave-113It was $20 for the first 30 days and I totally expected them to try and upsell or nickel and dime us, but they did not.
It really only was $20, after that first months it would have gone up to 60ish IIRC, that was for a non covered spot for a 32 foot class A.
They even had a dump station we could use when dropping off the RV and picking up again.
There's a bunch more places out that way.
I hope this helps a bit. Let me know if I can help in any way.