@davidhohn I understand it (i.e., this is just what I've heard people say casually), to go into business for yourself you have to do the bureaucracy to get a VAT number and then set yourself up with an accountant. This obligates you not only to pay an accountant, but also to make sizable social security payments even if you earn nothing. It's way more complicated than merely doing a schedule C, or even getting a business license in your home state and paying sales tax. I have done both in the US.
I have always planned to "go official" when I was ready to work professionally, but I never considered that work might start trickling in in amounts too small to make it worth it. The initial hurdle is high enough that you might operate at a loss, not to mention the time lost. This is in addition to the usual problem of starting artists not making much to begin with.
I honestly have no idea what all this does to contracts, but I would imagine that drawing up a contract makes you "official," and therefore subject to all the starting costs and bureaucracy. I should talk to an accountant.
Don't even get me started on doing two tax returns. I love Italy but I'm not fond of the bureaucracy!