Generally speaking, locations where it takes more than 10 minutes to walk from the nearest station to the property, locations where it takes a long time to travel to the city, locations where there are few passengers at the station, locations where it is inconvenient to live, locations in regions where investors themselves are not familiar with, and locations where there is a high risk of damage from natural disasters.
There is also a high risk of high vacancy rates when investing in properties located along railroad tracks or near highways.
If all or many of these conditions are included, it is probably safer to not invest in real estate.