I just need a cheap alternative.
Most Helpful Girl
You won't ruin it completely but you'll definitely harm your hair. Your hair will be harmed no matter where you go, highlights are still chemicals. I suggest you go and get them done professionally. My mom tried to do highlights and it came out the wrong color and bled throughout her hair. Highlights aren't easy to do. It usually takes the professionals sometime getting used to doing them and getting them right so I'd assume a home treatment wouldn't go so well.