Another dog question..

I came here the other night with a picture to identify a dog. I was looking for a boxer. I was able to locate another person who wants to actually give one away (and this one seems to be a pure boxer). The problem is this dog has heart worms. Owner said she got the dog 4 months ago (dog is 3) and the owners before hadn't taken care of the dog. She took it to vet and it tested positive for heart worms. She got the dog up to date on shots but couldn't afford heart worm treatment.

What am I looking at if I get this dog as far as cost of treatment, etc.