Anyone own a rental property?

Seems like the majority of people have had more negative than positive experiences with this. I asked on another forum and got about the same ratio of negative responses. Someone brought up a good point that with houses being so cheap right now, the majority of responsible people who can pay their bills on time are buying and not renting.

I have a question though. How am I supposed to buy another house before I sell this one? I did a calculator on google and it basically states that I can only afford a home that's about the same price as my current home as long as I still have that mortgage debt. If I do the calculator without the mortgage debt, I can afford the dream home that I found.

So how is that supposed to work? Do they expect you to sell first and then go searching for a home to buy? I know how I am with money and I know I could afford both homes for a year on my own if I had to wait for it to sell. But I know no bank would approve that.