
Age wise he will have to be over 12 mths of age.
Cost will depend on where you have it down....if you phone the Boxer breed council they may be able to tell you at which Boxer shows they are doing heart scores.... if you have it done this way, it is around £ 8 , it may have gone up this yr.
Other wise ask your vet to recommend the nearest Cardiologist to you.... be prepared , you may have to travel
The scoring will be from 0 to 6.... a 0 or 1 should only be bred from....some breeders will breed from a 2 , but under exceptional circumstances, you must know your lines inside out!!!
Do you have the scores of your dogs parents, this may give you an idea of his score... and are you planning to breed your dog... other wise unless you have some concerns over his health, there is really no need to have your dog done... other than your own personal knowledge.