re: Best access to $30k?

You can’t afford the Watch. I’m not sure what you want us to say? Why not buy a $10k watch or $20k? Going full on $40k in your situation is rather absurd.

Interest rates are not low, it’s not going to be cheap to finance and yes buying at 0% has some financing costs already built in.

ETA: fwiw something like a heloc is usually the lowest interest rates as you are placing equity down to guarantee the loan.