Usually people get anxious and frenetic for new sources of income, to find new jobs, so they can maximize their patrimony as soon as possible, but many of them forget you don't accumulate wealth only when receiving money or being paid by others for a work. We can also decrease our expenses and stop third-partying tasks we can do ourselves, so at the end of a monthly cycle we will have earned more money to invest and make it grow overtime.
People create so many worthless fixed expenses nowadays. It can be monthly subscriptions of services they barely use, eating out too often, purchasing superfluous clothes, accessories and items in general just for vanity towards the society. Sometimes people have all the tools they need on their hands to finish a solid building, however, since they don't know how to use them properly, it will look like they constantly need more and more tools indefinitely.
Well less expenses, more money to spend on other more worthwhile things. So yes, you can say not buying is "earning" if you actually put the saved money on something that gain value.
I don't agree so much about refusing to "third-party" tasks. As you progress you'd want to be able to delegate/outsource many tasks to leave you with more time to then use to other more important actions. Time is something worth paying for.
It all matters about management of things on which it would really be just sensible act for you to do so on dealing with something which you can see for it to be useful in longer runs rather than on dealing up with something specially with expenses and not worth kind of spending which would really be putting you out on a big trouble once emergencies and needed of funds would really be happening.
Speaking about getting different various sources whether from other work or some investment or business then it is really just a casual thing or mindset of everybody.
Doesnt matter on what form and what way as long it could give out the chance for you to earn more then thats what it counts.