Mortgage comparisons can also distort the model if each quotation uses different assumptions. Compare the same purchase price, deposit, term, fees and repayment structure, then keep a separate case for refinancing uncertainty.
I would challenge the idea that management is what ruins the investment. If the property produces almost nothing once someone is paid to run it, the underlying return may already be weak. Self-managing from nearby can hide that because your time appears free. Selling is not automatically right...