There are many benefits to paid hosting, including that you would have your own unique domain name (for example when you build a website to sell PDF sheet music, the address would be www.mybandPDF.com instead of www.mybandPDF.limewebs.com).
This gives you a professional edge, letting your visitors know that you mean business, and that you know what you are doing.
To build a website to sell PDF sheet music, you need to have a way to receive payment.
There are many ways to receive payment for your products.
Here are a few options:
Paypal
Amazon
Have your own merchant account (This can be set up very simply in the Omni Site Builder. This option is more advanced than using a third party site.)
Using a builder such as the Omni Site Builder is easiest, as it is made for those who have never created a website before, and has full instructions to assist you to build a website to sell PDF sheet music.
The other hosting options will have different processes, and may be much more complicated. The learning curve there would be set a little higher.
To build a website to sell PDF sheet music, if you have never created a website before, you will most likely want to take the easiest route.