Purchasing a rental investment with old roof

[Brock Best]

Looking to purchase a single family home as a rental. House is in excellent condition other than the roof. It’s old and has previously had a roof leak but has been fixed and not leaking anymore. I will buy the home with a conventional loan with 20% down. Is the seller obligated to replace the roof? Can I purchase the house if the roof isn’t insurable and replace the roof at a later date?