I was wondering how difficult it will be to get an extension on my permanent residence, considering my circumstances. My Re-entry Permit (REP) will expire in Jan 12, 2019, and by that time, I will be 24 of age, no longer a student, and may yet to be employed.

I've been in Singapore since 1997, gained my permanent residence along the way, and left to the United States in 2013 for College. I achieved my degree this May 2018, and was planning to work in the States for the last half of the year, which means I will be back in Singapore in January 2019, before the end date of my REP. Would this be too risky? Would I have to go to Singapore a few months earlier to be employed for my REP to be renewed?
To my knowledge, the PR itself doesn't expire but the REP does, and if I am in the country at the time of my REP expiry, I will be safe to stay? Or if the REP expires does the PR mean nothing? I'm not sure my knowledge is entirely correct. I also would love to know if having family in Singapore would factor into my REP extension. My parents are now Singaporean residents and my sister has been working in Singapore for around 3 years as a PR.
I'd really appreciate any help or advice, thank you!