Thank you for sharing your experience. In your Specific example, you are actively improving the unit and then charging to make up the cost over time. That is normal and expected.

If you instead didn't make any changes to the unit, but charged "market rent" for it, you'd be an ass. Those landlords that are charging so much for a unit because they know people need housing and will pay whatever they ask are causing issues.

Making a profit isnt a problem so much as price gouging on a resource people need to survive is.