Is my data plan being more used up when i turn on my Wi-Fi hotspot?

I wanted to use my computer in my car to download music while i was waiting for my boyfriend to get out of work. But i won't have Wi-Fi in my car. So i was thinking about just turning on my Wi-Fi hotspot on my iphone 5. If i do that will that use a lot of my data plan?

Yes it will

Yes Offcourse

Yes, and No. It will really depend on what your data plan says about using the phone as a HotSpot.
My plan which is a grandfathered plan with my cell company, allows me UNLIMITED HOTSPOT use, as well as UNLIMITED Tethering.

So your cell phone company and how they handle their Wi-Fi (HOTSPOT) usage is going to be what you will end up paying. Does your plan give you X number of Hotspot data or unlimited? If you are playing less than 80 bucks for you plan, I have a feeling your do NOT have unlimited HOTSPOT usage, and you better find out before you use too much data. If you have a limit amount of HS usage, you need to download an app that will monitor and alert you when you are getting close to that limit (if any).