If you're interested in COLLECTING sheet music or vinyl records here are some articles with useful information: 

Collecting Sheet Music:

http://www.collectorsweekly.com/music-memorabilia/sheet-music

http://www.parlorsongs.ac/insearch/collecting/collecting1.php

Collecting Vinyl Records:

http://www.collectorsweekly.com/records/overview

http://www.chicagotribune.com/lifestyles/sc-cons-0122-vinyl-record-collecting-20150116-story.html

https://www.digitaltrends.com/home-theater/how-to-build-and-preserve-a-vinyl-collection/

https://recordhead.biz/vinyl-record-collecting/

https://www.wired.com/story/new-to-vinyl-records-shopping-what-you-need-to-know/