While Kiddushin is a necessary step in a Jewish wedding, all marital obligations only apply after Kosher Nissuin (Rambam Ishut 10).

Nowadays we make Chuppah with some variations for Ashkenazis and Sefardis. I'd like to focus on the standard Ashkenazi tradition:

• Signing the Kettubah
• Walking the couple into under the Chuppah
• 7 rounds for the bride around the groom
• Kiddushin ceremony
• 7 Brochos and breaking the glass
• Cheder Yichud (staying in a secluded locked room usable for marital relations).

Let's take the husband's monetary obligations to heal his wife (I think it's better than burying or paying a ransom). I imagine that at any stage the bride can have, say, an asthma attack (or break a leg or worse).

After what stage exactly would the husband be obligated to pay his wife's medical expenses?