I deal with Bull calves that the dairy industry dumps. Anything from 1- 10 days old. Putting money into these calves is a huge risk. Many did not receive enough colostrum and end of very sick no matter how hard you try. Not to mention the risk of Phenomia. I can't count the calves I have euthanized that went down hill fast.
In my opinion, I would never buy one of those foals. Its just not worth it money wise nor the heartbreak if they crash. To me, with any animal there should be a minimum
of 10 days before they are pulled.