So if I built a house, then rent out a room to help pay the bank for the construction loan.... what does that make me?

Decisions can be made democratically among the residents themselves, and manage it collectively. Landlords lose their excess property, and choose the residence they want to live in

I have friends who live in a "co-op" style, multi-story building. They each own their own condo. They have meetings, bring up issues, and vote on them.

As to what happens to the people who currently own homes: They get an actual job, instead of leeching off of everyone else.

How to transform society into a landlord free society? The first step is to remember that the land itself used to belong to all people, then bit by bit it was transferred to landlords. Why do some people get to own dozens of houses while others own none? The land being a common resource is the natural state of things. Once you realise that, you can see how unfair the current setup is, and you will see the need to change it. If enough people see this, then society will change. At this stage, there's no detailed game plan necessary, just the growth of awareness. Lasting change happens from the bottom up.

Communism, and then instead of a shitty landlord, you have a shitty municipal housing employee who power trips and starts fucking with you and ignoring your complaints about no hot water or no electricity.

I fucking despise the pain of our current system, but honestly people are delusional if they think replacing it with DMV employees is going to end the bullshit they deal with. People generally suck, especially when they hate their job.