Have a look at Accommodation in Florence for an overview - there's a link to a website where you can look for accommodation.
Yes, you will need to organise accommodation before you arrive. However, I don't think this means you have to actually sign a lease - you can book yourself into a backpackers at first, for example, and take proof of this with you, as well as a letter detailing your plans for finding accommodation, when you apply for the student visa. You chould give your local embassy a call to double check on this point. Where are you moving from?
There are loads of online apartment websites to start you off. Be prepared to be shocked at the price though - a lot of tourists go this route which drives up the price. Try these guys for example: http://www.oh-florence.com/en/florence-apartments/ or this one http://www.apartmentsinflorence.net/
Expat Health Insurance
Cigna Global Health Insurance.
Medical insurance specifically designed for expats. With Cigna, you won't have to rely on foreign public health care systems, which may not meet your needs. Cigna allows you to speak to a doctor on demand, for consultations or instant advice, wherever you are in the world. They also offer full cancer care across all levels of cover, and settle the cost of treatments directly with the provider.
International Movers. Get Quotes. Compare Prices.
Sirelo has a network of more than 500 international removal companies that can move your furniture and possessions to your new home. By filling in a form, you’ll get up to 5 quotes from recommended movers. This service is free of charge and will help you select an international moving company that suits your needs and budget.