One of the best ways to build wealth is to get a handle on your finances by signing up with Personal Capital. They are a free online platform which aggregates all your financial accounts on their Dashboard so you can see where you can optimize. Before Personal Capital, I had to log into eight different systems to track 28 different accounts (brokerage, multiple banks, 401K, etc) to track my finances. Now, I can just log into Personal Capital to see how my stock accounts are doing, how my net worth is progressing, and where my spending is going.
One aspect you might want to add to your scoring is “inflation protection”. At one end, bonds and CDs generally pay a fixed nominal coupon that doesn’t rise with inflation. Stock dividends and Real estate rents (and underlying property value) tend to. Not reallly sure how P2P lending ranks- though I suppose the timeframes are fairly short (1 year or less?) and therefore the interest you receive takes into account the current risk free rate + a premium for your risk. Now that I think about it, P2P lending probably deserves a lower score in the activity column than bonds too (since you probably need to make new loans more often).
My favorite type of semi-passive income was rental property because it was a tangible asset that provided reliable income. As I grew older, my interest in rental property waned because I no longer had the patience and time to deal with maintenance issues and tenants. Online real estate became more attractive, along with tax-free municipal-bond income once rates started to rise.
I personally haven’t tried any of the below methods so I can't speak from experience to how they work. In my mind, the most lucrative way is through building a REAL business online and providing your visitors with great value. However, after some thought, I decided to include these here because, quite often, the biggest roadblock for many is a mental one: believing that making money online is possible. From my experience, once you have made your first dollar, or even your first cent online, the world is suddenly a different color.
Many new real estate investors take out a conventional mortgage on their first property, paying between 10% and 30% as a down payment. While a higher down payment will decrease your payment and increase your immediate cash flow, it will likely reduce your return on the money you put up. Most with good credit scores should be able to get a conventional mortgage though interest rates on rental properties are usually higher than owner-occupied home loans.