Note: I'm NOT a CPA, or even remotely qualified to offer tax advice.
What is legal for me may not be for you. I own a business and have a home office, so I can do more of that type of stuff than most people can. I didn't want to give the impression that I'm filthy rich and have money to burn, as that's FAR from the case.
Any business that relies on the Internet at all should have multi WAN, especially if you're reliant upon lesser quality connections like cable or DSL.