There are also two other ways to pay for a first degree: scholarship/sponsorship and parents' CPF.

I'm also from poly and thought of signing up during NS but in the end chose parents' CPF to pay for a full time degree. Used all my savings and army allowance and some academic part time jobs for expenses during my study. I paid my uni+poly+laptop debt within 7mths after graduation. It's possible but one must be frugal. Didn't spend on unecessary stuff like extra clothes, new handphones, "expensive" dining (incl fastfood), etc. Live a simple life and focus on study/work for that 4yrs.