Booking a service at your home asks for the visit address and a saved card. The address tells your practitioner where to go; the card confirms it's really you. You're not charged when you book — only once your visit is under way.
When you book a service performed at your home, you'll be asked for the address for that visit. It sends your practitioner to the right place, and it's saved with that specific booking — if you move or update your profile afterward, an already-booked or past visit keeps the address you gave at the time.
You'll also be asked for a phone number your practitioner (or the studio) can reach you on that day — useful if they're running late or can't find the entrance.
Some home-visit services require a card on file before you can book. Saving one doesn't charge you anything at booking time — it's simply proof, similar to a hotel holding a card at check-in. It also means your practitioner isn't sent to a stranger's home on the strength of a name and email alone.
You're charged once your visit is actually under way — not when you book, and not before your practitioner arrives.