You can use residential broadband for a small office, just get a deal which give you a router for connecting more than one PC.

Accessing your home email accounts, well if all you need is an internet connection to do this then you are fine.

The business broadband packages you might find are easier to setup email accounts with your company name on, but you can buy such services third party such as this one https://mail.theimps.com/src/login.php