Currently we have a duplex and a condo that we rent out. I manage the properties myself so it does take a little time. The rental properties are mostly passive, but I have to do some work occasionally. Recently, I had a tree trimming company out to trim the maple in the back and remove some dead arborvitaes along the fence. We decided to replace the arborvitaes with potted bamboos to help screen the property. So this past weekend, we split a pot of bamboo and planted some mint in the garden. That one sentence sounded easy, but it took us 3 hours to do. We carted an old pot of bamboo from our balcony and it was a struggle. That thing must have weighed 100 lbs. Anyway, we’re willing to put some work into the duplex because we plan to relocate there at some point. Also, the rental income shows up as negative income in our tax due to depreciation. That’s a nice side benefit to being a landlord.

I get excited every paycheck because I know my investments are going to increase by a decent chunk. I use Mint to keep a close eye on what the current value is at and make goal marks to hit. Every time I hit a goal, I do a little happy dance and decide what I want my next marker to be and when I want to hit it by. I’m nowhere close to being financially independent or even debt free, but it’s exciting to see the ground work being laid and watching it grow.

Speaking of selling stuff online, that's another mostly passive way to generate income. You could generate an income stream for a while by clearing out your basement or attic and selling items on eBay or elsewhere. This can be especially effective with collections. If you have lots of games or jigsaw puzzles that are taking up space and not being used, they can be great sources of income. You might reap a lot by selling new and used clothing you don't need.
became $1,000,000 during an 18 year period (about 3x better than Berkshire Hathaway). Five – ten shares, or more, invested in a ROTH Ira and held *consistently* come h..l or highwater, with dividends and splits reinvested, may provide you a very pleasant surprise in 20 years or so. Asset Managers often do better than the assets they manage. Eaton Vance (EV) and T. Rowe Price (TROW) also did exceedingly well over a 25 year period.

Why did P2P lending get a liquidity ranking of 6? It is quite possibly the most illiquid investment option you listed. You said you rank liquidity by “difficulty level of withdrawing your money without a massive penalty”, and for Lending Club notes, it’s not only difficult and extremely time consuming to sell all of your notes in their super illiquid market, but you would have to sell your notes at large losses to hope to get others interested in buying your notes. On top of that, it is impossible to withdraw your money any other way other than just waiting for interest/principal to pay off every month until maturity in 3 to 5 years. You can’t just one day tell Lending Club “I want to quit, please give me my money back.” One can even argue that it is less difficult to sell a home (in order to “withdraw” the money invested) than to withdraw all of their money from a P2P loan portfolio because it is very possible to sell a home before 3 to 5 years.
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.