If, as you say, you want a proper business network then fiber IS the way to go. The infrastructure cost/installation time compared to copper is minimally different and will be claimable on tax. When buying your network peripherals spec fiber NICs or just buy secondhand AT2701 10/100s for a tenner for your workstations and printers and you are future proof and as secure as it's possible to be as a "normal" person/business. Copper infrastructure is not the way to go at all. In your lifetime there is absolutely no way you will run out of bandwidth on a fiber network in your house unless you are intending to rival Google in the amount of traffic you will have