I have bought 5 places near Independence MO and one place in Bullhead Arizona in the last few years. Prices ranging for 40K to 110K 3 are duplex and 3 are single family rents range from a low of $550 to a high of $800. So somewhere between 1.3-1.7%/month.
I read Mayor Pete book and his mortgage is $450/month. He's fixed his place up but looking at rentals in South Bend, IN, I bet he could rent it for 1500-2K a month that's a pretty nice return. I found 4 places in South Bend, on the first two pages of Zilliow that were well above the 1% rule. I was recently on a Costa Rican tour with folks from IA, PA, OH, WI, ID, and rural IL, and TX and everyone of them had real estate that was 1% rule.
My SWAG (scientific wild ass guess) is that you give find rentals in parts of 30 out of the 50 states. that meet the rule. Pretty much everything below the Mason-Dixon like excepting VA. The whole rust belt, small city Texas, except for Austin suburbs and maybe Dallas or Houston suburbs. The plains states, scattered places in NM, AZ, UT, and NV. Where I don't think you can find 1% places is the West Coast, New England, and most of the Atlantic states, and most cities with a population over 1 million. Although I'm far less certain my 1,000,000 population claim.