Most states let you finance the tax, but it raises your monthly payment and total interest. Paying tax in cash up-front saves the interest on that amount.

Auto APRs vary from ~3% for top-tier credit to 15%+ for subprime. Check your credit union — they consistently undercut dealer-arranged financing.

Yes, but you pay more total interest and risk being upside-down — owing more than the car is worth — for longer. 60 months is a common ceiling; 72+ is a red flag for most buyers.

20% is the traditional target. Anything less and you may owe more than the car is worth as soon as you drive off the lot, especially on new cars (which depreciate ~10% in the first year).

Private-party sales usually net more, but trade-in offers convenience and (in most states) reduces the sales-tax base by the trade-in value — sometimes enough to close the gap.