If there is anything a collector like to do besides collect is talk about their collection. Many collectors gather in specialty forums to discuss their hobby. Find a forum dedicated to the sport you are looking for and a discussion about autograph collecting will be posted.
Just about any auction site will have a large community of autograph collectors looking to buy memorabilia. Do a search on eBay and you will find thousand of listings with plenty of collectors bidding. Sports Memorabilia shows will also be a magnet for autograph collectors.
A philographist collects autographs
You can sell autographed albums to record collectors. You can also sell them to fans of the person who autographed them. Another person who would be interested is one who collects autographs.
There does not appear to be a name for it.
Weird
Quodophile.
Phonographer.
Someone who collects everything would be called a hoarder - this type of person may have OCD as well.
Some of the names given for a person who collects trains:model train collectormodel train enthusiasttrain modeler
That's an entomologist.
usher
Gun-collector
The person who studing about the shell is calles as chonchologist.