What I've noticed after 3 years in a low COL area that had peak population in 1950: minimum wage and/or public rental assistance seems to puts a floor on rental prices. This "floor" isn't so obvious in expensive areas, but where asset prices are low (due to shrinking population, lack of national bank activity, low employment, or whatever reason) this "floor" makes being a landlord more attractive on paper.
Where we are (western NY State near the PA border), there are $500/mo 2br rentals but they tend to be pretty run down. In decent shape, $700/mo for a 2 bedroom is very do-able. Decent, not fancy. Median house price is around $75,000 for our county, so plenty of sub-$40,000 properties that are habitable on MLS. This *is* a two-edged sword, as property taxes tend to be higher in lower-asset-value areas, at least as a % of house value (often can be similar on a per-capita basis). Don't forget to include/adjust for taxes when running rental math!
I have seen some areas of the country with much lower rental rates (where no "floor" seems to apply), these areas tend to be seasonal or have few lower-income folks (yes, that seems counter-intuitive). In our area, some "nicer" neighborhood rentals are actually less expensive than rentals in lower income neighborhoods, since the "nicer" areas are less walkable and folks assume they must have a car (even if MMM folks know better). Does suggest that folks are being rational in calculating total out of pocket expenses ;)
Imo it is critical to be local yourself or have a trusted partner who is. Some localities require a local agent/manager if the owner doesn't live nearby.