I would have to say never, unless you’re growing into a company that’s simply way too large for one person to manage. If you’re only in the beginning stages, you don’t need a professional service to help you with the online marketing process (or anything related to your website); you can just use free SEO tools and you should be able to make a name for yourself. Most people remain a one-person operation until they’ve started to turn a decent profit, and the work becomes too much for one person to handle. If one person has a grip of everything, there’s really no need to bring anybody else into the process. You made the site and had a goal in mind, so why would you have someone else come in and risk everything (and potentially try to change the direction of your website).
You know you need professional help when you’re failing to meet deadlines, all the meanwhile trying to keep your finances in order. Not only that, but the server for your website is going to grow as the demand for your product does – so you might need professional help in that regard. You can’t be everywhere at once, so when you’ve reached the level that other companies have, you’ll need to bring in professional. That’s something a lot of us don’t want to hear, especially the budget-conscious ones, but it’s true! Do you think Bill Gates knows about absolutely everything that goes on in Microsoft? Well, probably, but he has people he can delegate certain jobs to. If he didn’t, there’s no way he would have enough time to handle the things that he does. seo-is-war.com have released a great list of free to use SEO tools for 2017 – we highly recommend you check it out.