Profit, profit, I’d say reasonable profit and mandatory standards.
For example, when I lived in sweden I knew a landlord, he was stopping because you beeded around 50 appartments (might be inflated from his side, but in many countries you can live off of 2 so …) to make a decent salary.
In sweden you cant rent out a shitty appartment, you cant set the rent as you like it, and youre taxed etc. etc.
I mean it should be like a normal job, not granting you robber rights.