This past summer I interned at a company which then offered me a full-time position for after I graduate in June. I am very glad I have this offer, however there are a couple issues I have:

1. The company is out of state, and I would rather work in my current state.
2. I believe the compensation offered was a bit low compared to what I could find elsewhere, and their state has state income tax while my state does not, making my take-home pay even lower. Using Glassdoor's market worth calculator tells me that the offer is ~11k lower than average in their location, and ~20k lower than my location.
3. While I enjoyed my work, the company is not rated super well on Glassdoor (< 60%).

My response is due in a month, and because I believe I could find a job that would be a better fit for me I do not want to accept it and settle for the job. However, I do not want to decline it either in case I do not find anything better. Is it unprofessional to accept the offer while still looking for jobs, and then cancel if I find something better by June?