Glossary
Opportunity cost
What you gave up by choosing this instead of the next best thing.
Opportunity cost: what it means in practice
A side hustle netting $800 a month for twenty hours a week is not free money if those hours could have gone into skills that raise your salary by $20,000 a year.
It is the most consistently ignored cost in wealth-building, because it never appears on a bank statement. Every technique on this site should be judged against what else those hours and that capital could do.
Price your hour before deciding. On a $70,000 salary an hour is about $34 before tax. A weekend project netting $300 for twenty hours pays $15 an hour, so the honest description is that running it costs you $19 an hour - which can still be the right call, but only if it is buying a skill, an audience or an asset that the salary does not.
The version that matters most is capital rather than time. $20,000 as a deposit on a property, as inventory, as an advertising budget or in an index fund produces four different lives ten years out, and only one of them asks nothing further of you. Every technique on this site is a choice against the other three, and the comparison is the whole decision.