I’d like to mention that Rush Rally 3 has premium content (some cars, some locations, and the right to play time-limited live events), but it is reasonably priced in my opinion. Grid Autosport on the other hand has all the DLC packs from the console version for free. Both are fantastic speaking as someone who primarily plays on mobile due to general loss of interest in current console/PC games.
My wild guess is that AC Mobile will be a paid title. It’s also mentioned that it’s in development only for Apple, so it’s possible that it might be on the Apple Arcade subscription service (as far as I’m aware, no games on Apple Arcade have in-app purchases). I wouldn’t rule out a model like what Raceroom does either.
Just tried this and drove a handful of laps with the standard Abarth 500 EsseEsse around Silvestone. With the lap I did, I thought I was contending for Britain's Worst Driver but checking the leaderboard, it's the world record . So hard to drive, doesn't seem like many people have attempted it yet. This game makes Assetto Corsa PC version physics feel like it was designed for beginners, so much oversteer makes it difficult to drive properly this version! I hope they make it more driveable as it is not enjoyable as it currently is. Maybe fully upgraded cars will be easier to drive.