I presume you're mostly talking about passive investment from financing, as opposed to "write an ebook" or "make a course". I know you said "real estate" but R

I presume you're mostly talking about passive investment from financing, as opposed to "write an ebook" or "make a course". I know you said "real estate" but REITs are interesting and quite complex because they specialise in the sort of real estate being allocated to. For example, there are REITs for warehouses, storage, residential property, retail property, logistics, etc. The majority are not listed as ETFs and trade as regular limited liability companies so you have to actually look. They pay quite high dividend (5-6%) but are illiquid and require long holding periods. Landbay, Funding Circle, Zopa, Market Invoice, etc are all p2p shops for different sorts of lending or factoring, but I hardly see the point since the returns can be replicated by holding corporate bonds, with less risk and more liquidity. Maybe with the exception of invoice factoring. Crypto is interesting since it's non correlated to the main market but it's also not an "investment". I.e. there's little systematic reason to believe in positive returns over a long run. Paying down your debts is also obvious if you have a house loan or student debt since it's at least not a loss you need to keep incurring for interest payments. Investments uncorrelated to the market quickly become market investments so alternatives are pretty hard to find. For example, you're kind of wasting your time with building your own miner since there are multiple miners listed as public stocks readily used as proxies for profitable mining ... The same holds true for a multitude of other activities. So generally whatever you come up with, I'd suggest first thinking "is there already a public stock that represents this activity and does it behave as I'd expect a good proxy for this activity to behave".