Rescue vs Safety of Own Parrots

I made the mistake of looking through Craigslist Adds and some something that truly horrified me. A pair of cockatoos, 1 Goffins and 1 Greater Sulfur Crested living in a dirty and rusty cage not even fit for a cockatiel. They both lived together and the woman was "graciously" throwing in peanuts for them to eat when you purchased them. You could purchase 1 for 250 or both for 490.

Their feather condition looked horrible, but especially on the greater sulfer crested. My heart broke for them and I was seriously considering calling her but I feel responsible for my own parrots. I have 2 parrots not even a year old and a 6 year old. What if I brought something home. I know quarantine is a necessity but I also know that unless they are in a separate space that isn't sharing air, you aren't home free. By the time vet blood work would be back, I could have contaminated my entire house.

I was going to post a picture, but I thought it would just incite a ton of comments about how horribly they are living and not the question at hand.
The add was posted on July 1, so they very well could be gone even though the add is still up. I didn't want to call yet because I was afraid I'd just agree on buying them before I gave it rational thought.

My question is to those who rescue birds on the forum. What steps do you take to safeguard your own pets. Is there any way to avoid risk?

I have a quarantine room,separate air ,well away from the other birds, you can never be too careful. In the near future i will have a out building that will be the quarantine building. Right now it's the nursery ,but need a new one,too hard to keep sterile.

I quarantine in a separate room for 30 days. A seperate building would be ideal, so they're not breathing the same air but for me it isn't an option.

Well here what I do. I have a detached garage so weather permitting I use it for quarantine(it is not insulated so if it's too hot or too cold I can't use that option). When I got my Caique (a breeder who couldn't breed any longer and had a 6 month old to rehome), I went to the woman's house with a friend. There I took the blood samples necessary to send to the lab and my friend took the bird to her house to quarantine. Once the bird was cleared, I took it home.