We have phrased this as two questions but there are, in fact, three since the custom-built website can be divided into two topics.
Your website represents your business. It must show who you are and what you offer. To achieve that, you need to have a very clear idea before you start of exactly how you want the website to look and what you want to appear on it. That does not – necessarily – mean that the website has to be custom-built from the ground up, but we’ll look at that option first.
Do you understand HTML coding? If not, a do-it-yourself website may be beyond you. Yes, Word and other common software can produce a web page version of what you’ve written (to test this, write a document in Word and using the Save As command choose Web Page) but a thorough understanding of coding is necessary to really get the appearance you want. So you subcontract the job to a web designer – but now you have the task of making sure that s/he understands the picture of the ideal website that you have in your head, and then the task of ensuring that your instructions are followed.
There is an abundance of templates available – find them on the Web – and they will help you overcome your lack of coding expertise. They will also get you online quickly. The drawbacks include the risk that your website looks like thousands of others and the fact that any changes you want to make subsequently will be difficult.
And so we come to the third option, which is in many ways a more complex and rewarding version of the template: the full-blown Theme. There are professional Theme designers who produce what amount to ready packaged templates with a whole host of options, alternatives and add-ins (including e-commerce options). For most people, a packaged Theme is probably the way to go, but don’t compromise. Choose one that gives every single option you want and can be made to look the way you want it to.