I think it really depends on your school/work schedule and your dog. I'm a grad student, and I have 3 dogs, 3 cats, and a daughter (but I also have a husband to help me out). If you are planning to work more than part time AND do grad school, I'd say don't get a dog, get a different kind of pet (like a cat) instead. School has always been very "easy" for me so I was surprised how much work a PhD program actually is.

However, despite all the work, most of it can be done at home (which is why we can have 3 dogs without any problems). I'm home most of the time, except for class time and when I work out of the home. For paid work, I don't have anything very time-consuming because I would not have time for school then. I work one night a week as a piano teacher, and do some work from home when I get projects, as well as some work as a researcher occasionally (out of the home). I feel like I have more flexibility as a student than if I worked full time, but in your field you may need to do internships, etc. If you're unsure, you should probably wait on a dog. Are you going to go for a PhD in counseling psych or a PsyD?