I googled Canine Asthma because I had never even heard of dogs getting it. From what I read, it is rare, usually a reaction to allergies. It's also something that happens later in life: 2 years or older. It's even rarer in puppies.
Here is one of the links I read:
http://www.ehow.com/about_4673062_canine-asthma-symptoms.htmlI would be concerned that the condition really isn't asthma and is something more serious. Puppies with heart conditions can pant alot and will get winded quickly. Wheezing during eating might mean something wrong with the palate or esophagus.
The problem is that the pup's condition could be severe enough that a regular vet might not know the real deal. But most certainly, I would do a vet visit BEFORE taking on the puppy. The puppy may be free but you could end up with a huge bill in future vet expenses depending on what the real issues are.