You'll need a modem if you want to tap into your office network. You can use a modem or fax-modem to send documents electronically to your office for support staff to print and forward. Printers make it possible to preview new or revised documents on paper before you send them and to print faxes received electronically. Laser printers cost more. They allow you to circumvent the office entirely when you need higher quality printing.
Some attorneys get by with couriers and local fax and printing services.
You also need to explore whether you need a second phone line in your home to accommodate business calls, faxes, access to your office network, and data retrieval. If you want to connect to the Internet, check with your firm or local network services to find out what that will cost. Check software license agreements to find out whether you can use your office copies for home use. At a minimum, you'll need word processing software. You'll likely need communications software too.