With $200,000 a year in passive income, I would have enough income to provide for a family of up to four in San Francisco, given we bought a modest home in 2014. Now that we have a son, I'm happy to say that $200,000 indeed does seem like enough, especially if we can win the public-school lottery to avoid paying $20,000 to $50,000 a year in private-school tuition.
Finally, make sure you can service multiple types of clients. This is the best egg to have. Even for something as simple as a dog walking business, you can service multiple types of clients. For example, you can offer a puppy walking service and an adult walking service. You can have weekends at the park services. You can offer to take the dog to the groomers. Try to meet client’s individual needs.
Overall income potential: Excellent – Although it’s very possible to make $0 with a niche site if it doesn’t receive traffic, you can also make a lot of money if you rank well for good keywords.  It’s not likely that you’ll make a living off one site, but they are generally easy to build.  If you can build one successfully, you can probably build several more.
Anthony, nice setup! To your question about the rental mortgages, you haven’t said what interest rate you are paying. As a start, if you are paying more than the risk free rate (Treasury bills) which you probably are, then a true apples to apples comparison would be yes, pay off the mortgage. But, if you are comfortable taking more risk, you have other options to invest in which you *hope* will yield you more over the coming years. You also didn’t say whether the rentals generate net income and if so, how much? What is the implied rate of return on the equity you have invested in them? If you pay the mortgages off, you’ll have even more equity tied up, will the extra net income make that worthwhile? Maybe you should use the money to buy more rentals instead, if purchase opportunities still exist in your town. … this is less of an answer than a framework to analyze the decision, hope it is helpful.
The second category of passive income is drawing on sources that do not require capital to start, maintain, and grow. These are far better choices for those who want to start out on their own and build a fortune from nothing. They include assets you can create, such as a book, song, patent, trademark, Internet site, recurring commissions, or businesses that earn nearly infinite returns on equity such as a drop-ship e-commerce retailer that has little or no money tied up in operations but still turns a profit.
For a person working for a wage, their source of income is their job, or their labor (aka their time that they sell to someone). But you can own a house, and rent it out, and when your renters pay you renter every month, the source of that income check is your rental property, or your house. It would just be called rental income. If you have money in the bank in an account that pays interest, those interest payments are another source of income. We can say the source is interest payments, or we can identify the asset that is generating rent, and say your money in the bank that is generating “rent” (aka interest) is your source of income.