Uh can you explain please? I was talking to Southern Indiana Dobermans via email. So I would like to know what it is you see that are 'red flags'?
I see zero available titling information. Upon digging, no information in dobequest or OFA. If they've put in the work and effort to prove their dogs are worthy of breeding, then they would be proud to share this information. That I can't find any of it is telling. They haven't even shared the registered names of either of their breeding animals...and they use improper terminology for basic breed-specific things.
The health guarantee involving NuVet supplements is a HUGE issue. In my experience, the only people hawking NuVet as part of their health guarantee are breeders who should NOT be breeding.
They may be very inexperienced, and that would make me uncomfortable. With a breed that can become a health and temperament mess if bred incorrectly, I would run far, far away from anyone not doing it right. If you decide you still want one of their puppies, wait for one of them to show up in rescue. It'll happen eventually.
BTW, I see your price complaint, and I hear you. Well bred puppies are EXPENSIVE, but there's a reason for that. On this website you will get encouragement to rescue or purchase from an ethical, reputable breeder. Buying from Southern Indiana would be neither of those things. Please reconsider your price point or reconsider buying from a breeder.