really can depend on the sport. Lottery funding has made a massive difference. Lots get very little reward unless they get a bit of success, some are lucky arranging personal sponsorships.
going back to the 80s and 90s before lottery funding Swimmers (I used to be a club swimmer and trained with a few Olympians) got next to nothing in grants , all relied on local companies for funding and sponsorship and families. A lot had to get part time or full time jobs, if you were outside the British squad then financially it was even harder to balance work, training and progression. Not to mention keeping your job when you needed time off to compete.
I doubt there are many non medallist Olympians in non elitist events that are getting rich! More money in all sports nowadays for competitions but again for a lot that helps fund their ability to concentrate on sport