There are two types of doctoral programs in psychology: Ph.D. and PsyD. Some Ph.D. programs offer tuition remission and stipends for the most qualified students. PsyD programs generally do not. Some grad students are supported by grants from their major profession (in exchange for working on research projects). Generally such grant money is for living expenses rather than for tuition remission.
So, when you are exploring various doctoral programs and deciding which ones to apply to, you need to find out about the number of students who are supported by the institution. If there is no support, then funding comes from student loans.