Finished the Tour, only upgraded the essentials, bought all cars (you only need the one's below A for upgrades), then somewhere by Fan Level 27 you'll have enough dough for all the upgrades.
Or finish the Tour, only upgrade the essentials, make a copy of your local save, make one set of purchases, reload, do the other.
Could be useful if online goes away November 8, 2025 since once you finish the Tour you won't be able to earn any more money (outside of challenges and dominating players, if that even stays online).