There's a whole world of webnovel platforms for that niche now. Sites like Wattpad and Radish have entire categories dedicated to billionaire romance, often free to read with ads or a daily pass system. The writing quality varies wildly, but the upside is that you get serialized updates and can sometimes comment directly to the author. RoyalRoad isn't just for fantasy anymore; I've seen a few 'System-Enabled Billionaire' mash-ups there that were surprisingly fun. Don't sleep on your local library's digital collection either, through apps like Libby or Hoopla. Mine has a ton of popular billionaire titles from major publishers available as ebooks and audiobooks—just need a library card.
That said, the 'free' model on the big serial sites often means waiting for new chapters or watching ads. I don't mind that trade-off for discovering new authors before they hit Kindle Unlimited. Some of the most viral tropes start there, like the cold CEO who's secretly a cinnamon roll or the revenge plots against rival corporate empires. The community notes and comments are half the entertainment, honestly, watching everyone lose their minds over a cliffhanger.