This summer, I want to earn money to buy sequencing software. I really enjoy arranging songs (as well as writing them) so I thought it would make sense for me to try to sell some online. Can I do that without being certified or anything? If so, are there any sites in particular that I should look into? (Is this even a good idea in the first place?) Thanks guys!
Feel free to set up an online presence to sell original songs, but I must caution that it takes years to develop a reputation and an interest in your music, so, do not expect to make much, if any additional money if you are just beginning.
Unless you obtain written permission from the original artists, it is illegal to profit off an arrangement of someone else's work. You would need to obtain written permission as well as notify the royalty company they are registered with in order to pay them their deserved royalties. Royalty payments come from sheet music sales, recordings, and performances to name a few.
Regardless, some companies pay out royalties bi-annually (some annually) so any money you might make this summer probably would not be seen for a year or so.
That said, I have a friend who writes little songs for video games and is able to make a little extra cash doing so. All of his pieces are original, and he negotiates all of the payments / invoices / contracts, so it would be wise to research more into those subjects. One popular site is "Newgrounds". Another popular site is "moddb" where you can look for work (to join a development team) but pay is not guaranteed.
I am certainly not saying that you should not try, I bring these points up to keep you out of court and avoid needing a lawyer.
No - you do not need anything to start selling your own songs online.
That said, it is worth joining a body like the Musician's Union, the Performing Rights Society or other industry body, as they can help you protect and benefit from your works.
I live in the UK and I rely on the Musician's Union to cover any legal or contractual issues that come up. I am also a member of the PRS so I can get royalties when my works are played. If you are outright selling songs and the rights to them, then this may be less relevant to you but if you are selling limited rights then you may still wish to collect royalties.