Replying to Park boots

Hey guys im a beginner park skier (can 180, 360, slide rails) I currently have my gf's dads old ski boots (will have to look when i get home what they are called i can remember atm,) they are a really nice high quietly race boot that i love for on trail and back country but as a park skier im assuming there not the right way to go as they are really really heavy compered to my all my buddys boots they just got (NORDICA Transfire R1) Im looking to grab something probably 2nd hand and cheap as i only just got out of college and started work so defs super poor lol.

Anything i need to know when looking for boots (weight, flex etc) I really have no idea

Im using nodica double six 2011 skis