It certainly would be easier with a spouse, but I'm single and making it work just fine. I have a dog walker come in one day a week and run home during lunch one day to let them out. I have 2 very small dogs, which cannot go more than about 5 hours without a potty break. 3rd year - well, that will require more days with the dog walker, or I might pick up a first or second year roommate and 4th year...that will be most challenging, but certainly doable.
Dogs sleep 16 hours a day, but need exercise, attention and if single, a backup plan and a backup to the backup should a vet visit be required, on an exam day. It is definitely possible and I would not change a thing - especially being single - for it is great to come home to a bundle of joy and a living thing that communicates with you and will curl up next to you while you study.
Mine are a bit older now, so it's perfect. I would not recommend getting a puppy at this point, unless you have support. They simply require too much of everything. I would seriously consider adopting an an adult dog that is house trained and already used to either being crated, or home for an extended period of time. It will make your life so much easier.
I take dog ownership very seriously, as I committed to these guys 8 years ago when I used to work from home, and will not let my current situation affect their quality of life. Just make certain you can provide for a dog in all ways (financially, emotionally and physically) before making the decision.
Best of luck!