First of all, aside from any other issues, I must comment that I am impressed with your willingness to accrue your own debt to assist your parents. That is not a mindset often seen in youth today.
As for approval process, are you currently employed? Without securing the loan by other personal property, such as with an auto loan, I would imagine that your income will be a major factor in evaluating their risk. For the same reason they will be evaluating your risk, think seriously about your ability to make all payments timely. One late will destroy your score. I agree with prior posts.... talk to them. I think you will have a better shot with a CU than a major bank.
As for FICO impact, it might not be that significant. It will first hit you for a new inquiry in the application process, and then if approved, will enter into your AAoA calculation with an age of 0. Yes, it will improve your mix of credit, which will be balanced against the inq and AAoA hit. So together, I would not expect significant impact. If the loan is short-term, it will most likely be paid and closed before you need your score for future purposes, so the mix of active installment credit will be short-lived. I doubt that it will hurt or help much, either short or long term.
My primary concern would not be short-term FICO impact, but rather the chance of long-term and serious damage should you miss a payment.
