My most blunt suggestion would be to hold out until you can get into a ph.d program so you wouldn't have to worry about borrowing large sums of money since most ph.d program offer tuition remission and a stipend. However......
Psy.D programs sometimes offer asssitantships, usually teaching assistantships. But keep in mind that theese assitantships often pay very modestly, and/or only cut-down slightly on tuition costs. Its not going be enough to support you. Only a handful of psy.d programs (Baylor, Pepperdine, Rutgers) offer real significant financial support through assitanstships. Talk to your specific program about any oppourtunities. Other than that, apply for APA fellowships/ scholarships via their website to help out. If military service is an appealing option, explore HPSP scholarship programs offered by the US Navy, Air Force, and Army. Part-time work may be possible for the first couple year (particuarly if its a research position), but it certainly wont pay all the bills.
You are correct, you should be concern about how you will pay back masive amounts of students loans. Generally speaking, getting into 150K debt for a career that will pay you about 60k-80k per year (on average) is pretty foolish.