I do feel you may be putting the cart before the horse so to speak.

Might not have the horse power for the loans..

I think you have the cart before the horse though- focus on getting approved for your FHA loan and start analyzing fourplexes.

You may be pulling the cart before the horse here, unless you've already received strong indication that the seller will even accept your offer (assuming you're doing FHA since you mentioned you didn't have 10-20% for down payment). 

She was bringing four quarter hourses, ten miniature horses, a donkey, four dogs, four cats, and a raccoon that always stays in its outdoor cage.I know why she was single.

You can't sell a horse farm to a preper or vice versa.

Others have commented on the costs of building an ADU, so I won't beat that dead horse.

I like eating out in restaurants, boating, golf, pets, horses, watching strongman competitions, grilling out, having, and going to, dinner parties, watching old movies, classic cars, music/concerts, eating healthy.  

I see us all focusing on the price and many of us are right that it is about the condition of paint and scope of work that lets us know if you are being cheated so I won't beat that horse. 

Will the property continue having someone else's horses on them?