House hacking Tax write off

[Kwame Knights]

i'm under contract for a Single family (1600 SQ FT) and it has a existing detached two car garage (800 sq ft) that i'm planning on converting into a in-law unit/rental unit. I'm think of using a 203k loan to rehab both units at the same time. The main house will likely take 60K to rehab and the in-law unit 50k (high cost because i have to run sewer and plumbing). I currently meet the requirements for being a real estate professional. Would I be able to immediately write off the cost associated with the separate rental unit? What are the pros and cons of bundling the rental unit rehab cost into my loan VS doing it separate using cash or taking out a separate loan?