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theoriginalharbinger t1_jaepy2o wrote

Nah. You can run the math, but I doubt it's going to make more than a $10 a month difference.

You'd run the math two ways:

  1. Finance the car. Keep 15k in a brokerage account. Every month, reduce the amount in the account by the amount due for the car note. At the end of the loan maturity, whatever's left in the brokerage is your "arbitrage."

  2. Pay cash for the car with money removed from your brokerage. Then, take the money that would have gone to the car payment (the same dollar amount) and put it in a brokerage account. Increase the account value by whatever the expected rate of return is.

The difference between 2 and 1 is the option cost for maintaining your liquidity (in the first example) / opportunity cost (second example).

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