It gets difficult, Patient, because entry point both specific to the house value and and other economic factors/trends of the ownership period. You have to weight the investors aptitude. What of rents in perpetuity once the house is paid for. Passing properties on to your kids if you have them.
“How about studies with all of them maximized?”
I think there are some people on this blog whose history provides case studies for having all of them maximized. I have elderly friends who never invested in anything but RE, never were tremendous income earners and they are doing pretty well. Good study there. They didn’t get there with one or two percent ROI.
I am not going to say there are no definitive studies. I guess I will shut up.