How much hair is needed?

I recently got certified during quarantine and since starting back I have had a lot of people interested! Of course their first question is price.. my question is how much hair is typically needed for fullness and how much for fullness and length? I know it will vary from person to person but I don’t even know a starting point as I’ve only done beaded extensions! I will be using covet and mane hair. I will offer a complimentary consult, but it’s hard to give a rough estimate if I don’t know a min of hair needed in the first place. Any advice or info would be great! Thank you all so much! I am so excited to be a part of this community and offer this amazing method!