If I were going into a commercial enterprise I would be inclined to install a second, separate line (cable or DSL) dedicated to the business and secured separately from my home network. It also makes accounting easier!
I would confirm with the ISP - either through reading their Ts&Cs or in conversation - that business use is supported and approved.
I would further be inclined to consult with / engage a professional if you are not sure about how best to set it all up.
SD