It's looking like The Sims 5, otherwise known as Project Rene, will be free-to-play at launch, based on a recent job listing.
As reported by fansite Sims Community, a job posting for a head of monetisation and marketplace from EA shared on the Maxis Careers page has shared some details on the monetisation option that will possibly be available in The Sims 5. The job posting is still listed on the careers page, though it can't be viewed at the time of writing. It lists the typical kinds of responsibilities you'd expect for such a job role, but most notably it details how The Sims 5's in-game marketplace might work.
"Own Project Rene’s in-game marketplace of content and UGC (free and paid), and manage a data-informed player-centric player purchase journey," reads one of the responsibilities. "Maximising value to players, optimising player spend patterns, and minimising player churn." Things could easily change by the time of launch, but the wording does potentially imply that UGC, or user generated content, can be paid, which might mean that there are plans for players to be able to earn money from the game.