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You have 50+ Student (debt) cards. Start by clicking Dashboard > Student Debt and paying it.

You'll turn cards worth 800 SIM into cards worth 500-10,000 SIM.

Sell what you want.

As for citizen mining, you already have the popularity needed to max out your 'new citizen chance' at 30%.

Also looks like you're then training your airdropped homeless/citizens into workers.

Again, sell what you want.

To maximise your citizen mining, you can get as many accounts as you want, buy the cards to get to 30% new citizen chance and funnel all your airdrops back into your main account.

I'm at 20 accounts lol.

Finally onto tax refund.

This isn't something I'm really doing, but 'sick citizen' cards have 1-3 tax refund.

It's more a long play, so just see what cards you can combine into combines that offer tax refunds.

Things like 'modern homes'.