You can absolutely do that. If you want to upgrade to a paid plan to get some of the features you want, then you can switch at any time through the My Products option in your account or with the help of a GoDaddy Guide. Once you upgrade your site will have all the same customizations and work that you've already put in place, just with the added features. See Website Builder plans and pricing for more info. MAKING PIGGY 2 CHAPTER 1 - PONY SNOW MAP | Roblox Piggy Build Mode
Such website builders are based on the business model called ‘freemium.’ This means that they offer a basic service absolutely for free. There are no time limits – you can use this tool as long as you want. But if one of the Premium plans is paid, you’re likely to get an opportunity to use your domain name and upgrade your website’s capabilities. But this Premium plan is not mandatory.
I should highlight here that, much like all website builders, SITE123 is not without cons. It’s a simple and intuitive website builder, but it is more suited to building basic websites. If you use only the free options, you won’t be able to create anything but a simple personal website with SITE123. Meanwhile, its free plan has no duration constraints, but limits storage space to 500MB and bandwidth to 1GB. How To Make A Free Website - Wix Tutorial