Twilight has a free version but it’s limited in features compared with the pro version and it’s not for commercial purposes, if you want a cheap rendering engine with very good quality and with perpetual license with lifetime updates and upgrades for free, I recommend you Brighter 3D, it’s intuitive and fast.
You can also use other softwares to render, D5 has a free version that can be used with commercial purposes, and the best option but that takes a bit more time to learn is Blender, you can achieve hyper realistic renderings with cycles or not so realistic but still a good quality with Eevee, it’s an open source software so you can use it for whatever you want, with blender you can make animations as well among a lot more things, it’s one of the best softwares I’ve used, unlike sketchup blender releases new versions every 5 months with major updates and upgrades, it’s becoming an industry standard, it was used to make some parts of the latest Spider-Man movie. iI’s unbelievable that it’s free.