Should I make my brother sign a lease before moving in?

[Lourdes Medina]

Hello, I am new to real estate and still finding ways where I can learn more such as reading and listening to podcasts.  Recently me and my fiancé just bought a house and his brother is planning on moving in come September. I thought this would be a great opportunity to start practicing on becoming a landlord for our future buy and hold properties.  I was wondering if it would be a good idea to write up a lease and have him sign it? Will this lease and rental income count as landlord experience in the eyes of a mortgage company?