This is a really difficult situation, but in my opinion, you have to do what you think will make you most happy. My impression from other grad students is that you're not in grad school for the money, but for the fit. Also, realize that you will be spending 5-6 years working with this person. If you don't feel like the program matches your research interests, you have to be amenable and prepared to not carry out the work you'd like. You may end up with debt, but in the long run, you will be able to pay it off and be super happy with where you are in 10 years.