Multiple Tenants on a Lease

Hello everyone,

I interviewed potential candidates for one of my rentals and here's the situation- a mom and her 19 y/o daughter are going to move in first, then eventually the mom's fiance will move in once they're married. I put down in the description that everyone over the age of 18 has to pay for the application process through Zillow (including credit and criminal history). The mom already submitted hers and everything is great. I'm going to have the daughter submit hers and put her on the lease. How do I handle the fiance? They didn't give me a date for the wedding/move in for him. Should I have him submit an application with the checks now? Do I wait and then add him to the lease later? Thank you for the help