Passion For BDSM
Think of this as a hidden XP bar. You can check your progress (roughly) on the card or the PC DoS potential development section. When you fully fill it, you get the option to embrace being either submissive or a Dominant with additional benefits.
Gaining Passion
Any time you engage in DoS training interactions with your sims that are neither Dominants or submissives already, you gain the experience. This can happen when engaging in club play or servicing in public devices for example.
Becoming Certified Dominant
You can put your experience to use to become a Dominant for free. You also receive all of the purchasable additional licenses such as the BDSM artisan or the Rancher. This path also awards bonus skill to reflect your previous experience.
Becoming Owned Submissive
The other path you can take is the one of a submissive. Apart from the bonus skill, you receive the financial compensation for a mid tier contract, without needing to meet the usual requirements. You contract will also be immediately put on the public auction roster, allowing other sims to purchase it.
