I have a 8 month old cocker spaniel and he is the most wonderful dog BUT please do not underestimate the work and commitment involved in taking on a puppy - it is a huge responsibility and I would think very seriously about whether your 17 year old son has thought this through………… it has to be a family decision.
I had previously always had cats, and they are a doodle in comparison!
The first few months are really hard work, and you simply have to put in the effort to ensure a well socialised, well trained and happy dog. Think back to baby sleepless nights, your house will never be free of mud and hair, no more spontaneous days out. My Ddog has eaten a chair, most of the cushions in the kitchen, shoes, skirting boards, but his chew toys are all in excellent condition 
You must factor in the costs - not just food and basic equipment, but puppy training classes, insurance, vaccinations, monthly fleas and worm treatments, neutering etc
Yes, there is nothing more idyllic than a walk with your in morning sunshine, but think about the driving rain, the wind, the snow, sleet etc
I adore my cocker - but they are not easiest breed, they are friendly busy little dogs who thrive on human and dog company. I am home all day and my Ddog follows me everywhere, we walk for around two hours per day through the woods and fields, he sleeps at my feet, likes to snuggle next to me (or on my lap!!), he welcomes me enthusiastically like a long lost friend when I return from a trip to loo!!! What I trying to say is, you can't leave a cocker spaniel on its own all day - it would not be fair.
Having a dog is the most rewarding thing ever, those big brown spaniel eyes, melt my heart everyday - but it is a big decision and you need to consider all the pros and cons. Will your son really be want to be responsible for a dog for the next 12 years ………