What's a good replacement for Google Play Music?

Google has been saying that YouTube Music is the go-to replacement for when Google Play Music goes away, but that won't work for me because YouTube Music doesn't give you the ability to purchase songs. The service I'm looking for needs to have an online store, it needs to have no monthly fee, it needs to have a way to transfer my existing downloads onto it, and it needs to have an app available on Android. What are some good apps that fit this bill?