I’m a 13 year old girl and I am good at singing and like to write my own songs, so I want to learn to play the acoustic guitar so I have something I can play to accompany my voice. How hard is guitar to learn and how much does like, the average guitar cost? I can already play the piano, so I can read music.
Sorry if this seems like a dumb question but I don’t know much about guitars much.
I learned about your age too, and two years later, I am rocking out, SELF TAUGHT! 
You can too! just keep to it! you are never too young. To answer your ?’s, Guitar is and is not hard, depending on your patients level, and determination, I honestly learned to play the One by Metallica solo in the first few days, to weeks just by reading tablature. The cost runs from a low $80 for a first act elec. TO a
$90-100+ for a squire stratocaster. Have fun and good luck! sorry for the non-specificnessessss lol