When we hear the word "freelance" we envision someone who goes out and drums up their own business, assignment by assignment... In the days of black-and-white TVs it was pounding the pavement, going door-to-door, beating the bushes, but now it's more likely Fiverr, personal networking, and social media advertising. At any rate, these folks are braver than most because they have made a commitment to live on the assignments they can find themselves and they know that there may be times of feast and times of famine... times when they may be waiting to get the next assignment before they can hit the store for beer and Cheetos.
This is the usual and customary interpretation of the word "freelance", but this is not the meaning of the word "freelance" in the context of Italian National Visas.
In your campaign to qualify for a Freelance Visa to Italy, you don't just say 'hey, ho, I'm pounding the viales of Rome to get a job as a web designer, so uh, gimme that Visa', oh no....
You must gather one (or more) legally executed hourly contracts for your services from businesses in your hot little hand. These contracts will have a start date and an end date and the rate of payment. These contracts taken together must add up to a pre-tax payment amount of at least 700 Euro per month or 8,400 Euro per year (as of 2019).
But don't get too excited just yet, because the contracts are just the first baby step. Next you have to take these contracts and some other legal documents from EACH of these companies who want to give you contract employment, and take them to an office within the Police Department (of the city where you'll be working in Italy) called the Questura, where they will review the docs to determine if these are real companies who actually have the wherewithal to hire and pay you.
(I've dumbed this process way down. Important points to take away are that the Questura is an office in the police department in Italy, where people speak Italian and probably don't have fluency in English... and that this process follows Italian law, which is not some subset (superset? any kind of set...) of English Common Law (as most of us English speakers are used to), so it's probably going to feel very chaotic to you. It may behoove you to engage an Italian immigration attorney to help you though the process in Italy.)
After about 10 days, if the Questura decides everything is A-OK, they will issue a document called a "Nulla Osta", which you'll bring with you to the Visa application appointment you'll have at a Consulate inside your home country.
If your application for the Visa is then successful, you will be be granted a Visa for the length of time that your combined contracts will pay you the minimum as stated above. To repeat - your Visa will last only as long as the contracted employers (altogether) will be paying you minimum amount.
Head spinning yet? More details here.