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.
Work in grocery delivery. Instacart is a company that will pay you to pick up grocery store orders in your spare time. The entire purchase and order takes place through the Instacart app, making it easy for you to pick up the groceries your customers wants and get paid. Like other food delivery jobs on this list, Instacart lets you earn a per-trip rate plus tips. Shipt is another service that will pay you to shop for groceries and deliver them to consumers in your area, so make sure to see if they’re available where you live.
So, where are we supposed to turn to make money the legitimate way online? This isn't just about generating passive income; this is also about finding ways and means to create an active income through the conveniences afforded to us by the internet that will not only help us with our debt obligations, but also empower us to save, invest and get really rich in the future.
Lending Club went public in 2014 and is now worth about $1.7B. They advertise P2P lending returns of over 7% for well-diversified portfolios of over 100 notes. I’ve personally been able to achieve a 7.4% annual return over the past two years in a completely passive way by investing in A and AA notes. Others have achieved a 10% annual return through relatively minimum effort.
Investing in rental properties: Another form of real estate investment, rental investments (i.e. becoming a landlord) could steer you down the passive income path of steady monthly rent checks that you can use to pay off a mortgage loan on the rental property. After the mortgage is paid off, those monthly checks go right into your bank account -- potentially for years to come. 
Tutor students. Many families prefer the flexibility of using an online tutor. Depending on your background, you could be simply helping a child with homework or providing college-level support. You need to have your own computer and high speed internet. Experience required differs among companies. Some require “strong experience,” while others require a specific educational background. However, most companies do require a college degree.
Better yet, you can even upload your own book to one of the world’s largest book sellers: Amazon. With Amazon self-publishing, you set the price, retain the rights to your book, and get access to Amazon’s massive audience. For every sale, you keep 70% with Amazon taking the remainder as a fee. If you want to get started, check out Leslie Samuel's great guide to selling eBooks online or follow Tara Gentile on CreativeLive as she shows you how to use your existing body of work to write an eBook within the next week. Who knows, you might just write one of the best business books of this year!

Or you can take dog walking a step further and get paid to take a dog in while the owner is away! Have you ever checked to see what it costs to board a pet? Those places are not cheap! Do some research and charge 10 – 20% less. Post your ads on Craigslist or around town. But don't expect people to just leave their loved one with a stranger. Make sure you offer your references and that you have all their necessary information if Fido gets injured or sick. Rover can help you here, too – Become a Pet Sitter.

You can make extra money left and right if you just know where to look. If you like to ‘tinker’ I’d suggest going to the DIY section on Pinterest. You can find thousands of projects there to make, and you can sell them at a nice profit. You can make 20, 30, or 50 bucks at a time, in real money. Not the ‘get rich online now!’ stuff you see around. I make old teapots into lamps, or old shirts into aprons and sell them locally on Kijiji or Craigslist. It’s totally doable. 
The biggest surprise is real estate being second to last on my Passive Income Ranking List because I’ve written that real estate is my favorite investment class to build wealth. Physical real estate doesn’t stack up well against the other passive income sources due to the lack of liquidity and constant maintenance of tenants and property. The returns can be huge due to rising rental income AND principal over time, much like dividend investing. If you are a “proactive passive income earner” like myself, then real estate is great.

Creating a video series and selling it as a digital download on your blog, much like an eBook, can be another great seller. A video course, teaching viewers a specific skill or how to achieve a particular activity, may well resonate with your audience. If you are going to go down this route then your videos need to be as professional as possible so you should consider investing in some video and lighting equipment, as well as editing software.
Truebill is an app that helps you save money by identifying recurring subscriptions and other bills and helping you cut costs by negotiating better rates and fees. One of their partnerships is with Acradia Power, which has the potential to save you up to 30% on your electric bill. It searches for better power rates in areas where competition is allowed, and it locks in the better prices for you.
If you have a spare bedroom, you can find a roommate or list the space on AirBnB for travelers. Having a roommate is the more passive of the two, as being an Airbnb host will require more work in the form of turning over the room between stays. This is a super painless way to earn $500 to $1,000 a month without much effort – you may even be able to cover your mortgage payment with this extra income!
Domain names cannot be replicated. If one is taken, the only recourse would be to approach the owner to discuss a sale. While there are other variations you could choose, sometimes owning a certain domain (especially if it is attached to your business) can be worth the premium. Often, people will scout out domain names that are still available, buy them, and then sit on them in order to sell them down the road. Depending on who may want the domain down the road, you could sell it for a large markup.
If you’ve ever wanted to try real estate investing but don’t want to deal with all the stress of being a landlord, you might want to consider investing with Fundrise. Fundrise is a new platform that allows you to invest directly in a real estate portfolio that a team of professionals identifies, acquires, and manages on your behalf. With a starting investment as small as $500, you get exposure to dozens of solid, value-producing assets.

It’s one of the oldest and most proven ways to make money – buy low, sell high. The buy low part comes from searching garage sales, estate sales, and even thrift stores to find items that are in good condition (“gently used”) but selling well below what they would if they were brand-new. In this way, you might be able to acquire an item for $5, and later sell it for $50.

There are loads of resources for making money online as an affiliate. You could source products from ClickBank, Commission Junction, Rakuten Marketing, Share-a-Sale, Impact Radius and many others. Plus, many of the larger companies have their own affiliate programs as well. Do your due diligence and find the right company with a relevant product or service to your audience that you can sell as an affiliate.
Take it seriously. Yes, you’re applying for an online job. Yes, you can do the work in your underwear, but that doesn’t mean it’s not a “real job”. You must treat it as such or they aren’t going to treat you as a serious candidate. You aren’t the only one who wants to work in their underwear. In fact, the competition online is likely higher than it is in your local area.
Hold a yard sale. If you have a yard or garage and plenty of items to sell, you can have a yard sale as early as tomorrow. By advertising your sale on local Facebook pages and Craigslist, you can also skip the paid newspaper ad and keep all of the profits for yourself. If you don’t have time to price everything, try asking patrons to “make an offer” or grouping similar items on tables with an advertised price (e.g. everything on this table is $5).

Robo-advisors are diversified investment accounts that are automatically managed by a computer algorithm (as opposed to a human money manager). If you want to invest, but don’t have the money, or don’t want to invest with a money manager, robo-advisors are for you! Robo-advisors make investing easier—and cheaper—so they’re perfect for new investors.