It depends, because you could have a certain skill (such as a bespoke shoe maker, which is becoming rarer these days) that markets clients in his/her region without a lot of help from the internet. But for it to grow it would need to of course build a website to reach more clients.
Whereas an online business like a web design, or seo company could do everything online and be dependent on reaching clients from online. But if it would like to grow it would want to employ physical workers, maybe even rent an office.
From both these hypothetical scenarios, both online and offline would need to be intertwined to grow the business and the difficulty of growth depends on the niche.
It also depends on the persons approach to starting from offline or online as some people prefer to be more 'hands on' with their business instead of using the computer for everything.