What is the best way to get platinum blonde hair?

I’m a male with almost elbow length brown hair. Parts of it were purple then died back brown, It’s not noticeable, but I don’t know if that will affect the process. I need to know from people who have tried or are knowledgeable in the area whether I could do it at home or if I NEED to go to a salon (If so, about how much would it cost) also, any specific things to look out for that might ruin it completely while doing it at home.