Thanks for asking. https://passiveincomemd.com/what-is-passive-income/ gives a good summary of the definition I use. But in brief, it’s income that isn’t proportional to the time you physically put into acquiring it. It doesn’t mean it’s not without work or effort. It’s just that most of the work is done up front and it continues to pay off long after that initial effort. Real estate fits into that box. There’s definitely a spectrum but compared to what we do as doctors, where our compensation is directly linked to our time, most of these things are quite passive.
After these tenants move out, I'm thinking of just keeping the rental empty with furniture. It sounds stupid to give up $4,200 a month, but I really hate dealing with the homeowner association, move-in/move-out rules, and maintenance issues. Given that the condo doesn't have a mortgage and I have to pay taxes on some of the rental income, I'm not giving up that much. The condo can be a place for my sister, parents, or in-laws to crash when they want to stay in SF for longer than a week or two.
Residual income is calculated as net income less a charge for the cost of capital. The charge is known as the equity charge and is calculated as the value of equity capital multiplied by the cost of equity or the required rate of return on equity. Given the opportunity cost of equity, a company can have positive net income but negative residual income.