If they're "labour-intensive" that's pretty much the definition of not passive. I suppose it's possible that you could invest significant effort into setting up an Amazon affiliates site or write a book or whatever and just let it run but most people aren't going to have a lot of luck with that. Generally speaking, passive investments require investing capital and then collecting returns from that capital.
> If they're "labour-intensive" that's pretty much the definition of not passive.
Generally it's understood that "passive income" on HN refers to income resulting from an initial investment of labor that continues to generate revenue with little to no additional labor input.
An initial investment - that investment can be labor or it can be capital or it can be both.
In the same way you can say "work at Starbucks part time for a year and then invest 100% of that extra income into an index fund for passive income" rather than "work on a book for a year and collect book sales as passive income."
That's fair enough. That said, it's generally hard to generate purely passive income by just investing labor. Software is somewhat the exception for this group but if you just write something and stop working on it, any income is probably going to decline fairly quickly.