I know this is late, but I would actually suggest that if he continues to push after you say you need more time, you should turn him down. There is a reason that most graduate schools agree to not force applicants to make a decision before April 15th.
In this case, if he pushes you to make a hasty decision, he likely does not have your best interests in mind. Any professor or advisor I know would totally respect wanting to receive a funded offer. It looks like you are in industrial engineering and statistics? I don't know about statistics, but for engineering my professors always tell me that one should never have to pay for graduate school; I would imagine similar may be true for stats. That said, if this advisor is being pushy for you to make a major life decision, forgoing all other outcomes well before you should have to make a decision, imagine working with that individual over the next year. or two years. or the next five years if you end up doing a full PhD with him. It sounds like he would not really care how things affect you if it meant helping his career. Maybe I am extrapolating too much, but I would not want to work with the person.
Edit: that said, you should definitely ask for more time. if he agrees to give more time, I wouldn't consider it an issue.