Unfortunately, a half finished website can be just as bad as not having a site at all. If the site isn't constantly updated, your customers won't be able to find the information they need and are more likely to visit another business's site to get their information.
If you don't have the time to keep all of your social media profiles updated and your website current, it is definitely worth it to look into hiring an agency to do this task for you.
Many agencies will be able to design the website you've always wanted, regularly post to your social media profiles, and even engage with your customers for you online. The best thing about hiring an agency to handle your online presence is that they will have professionals constantly monitoring your social media profiles and website who can respond to customers in a timely manner while you are able to run your business without sitting in front of a computer all day.
Hiring an agency to manage your online presence will obviously cost you some money. But when you factor in the time that you are saving and the fact that customers will always be able to access accurate information about your company, it is well worth the cost. It is also important to remember that many agencies are small businesses just like yours and they rely on support from the community just like you do. When small businesses help each other out, everyone is a winner!