Good Rental Applicant, but In/Out Family Roommate - Question

[Brandon Mattingly]

I have a good applicant for a 3/1 SFR I rent out who told me she would be expecting her mother to move in with her during the summer months but then leaving back "home" to her home out of state. My rental is in Indiana and the mother is based in Flordia.

I'm not completely opposed to the idea since the daughter seems like a great potential tenant and they both agreed to be screened as tenants separately.

My question is: How would I structure this lease and/or addendums?
Should they both be on the lease from the get-go? Should the mother be added in through a roommate addendum later on?

Just is an out-of-the-ordinary scenario, so just wondering if anyone has worked with good tenants who have temporary roommates.

Thanks in advance!