HDB 3 room but selling off as divorcing
OK, so where is your parent going to live after the sale?
May have a relationship but no plans for marriage
A partnership does not require legal marriage. Some of the most durable, enduring partnerships are between two people who never marry. That includes same sex couples who cannot marry in Singapore, at least. (They can legally marry elsewhere but with no legal effect to those marriages in Singapore.)
My question is really focused on whether you expect to have a partner in your life that you care about, and whether you will be dependent on each other. Whether you get married or not is not my question.
Since no dependents therefore no need to have any insurance except hospitalization
No, not in my view. Your life plan critically depends on your future earning potential, and so the other "big two" insurance is Disability Income Insurance (DII). You may have a couple million dollars of lifetime earnings ahead of you...or not if you were to become disabled tomorrow and unable to earn any of it.
Most likely depend on me but I wish to not care about it(Not gonna care about parent) since its parent choose not to save up and spend on gambling.
OK, but the reality is that you will care, because you're human. So I suggest topping up that parent's CPF Retirement Account (I assume this parent is age 55 or older; Special Account if below 55) for up to $7,000 now, with tax relief for you, and keep doing that every January. That'll put a lifetime income floor below that parent from age 65, and that'll be that.
I agree that it also sounds like you want to get out of the house. OK then, assuming that's financially viable, let's assume that.
I do not mind keep working (if my body allows to)
OK, and see above re: DII.
My plans were to stay in a 1+1 / 2 bed condo alone (or with GF if have) and have about 2.5k-3k income when retirement. (Hopefully able to fully paid condo before retirement so only maintenance fee + utility is a monthly expenses)
The safer, smarter play is to accept the government's generosity on a HDB BTO since that's such a heavy subsidy and too tempting to pass up, in my view. That puts you in a nice bachelor or couple pad with a 99 year leasehold, and you're housing secure for life. After the 5 year MOP you can take stock of where you're at in life.
A private condo simply means you spend a lot more to put a roof over your head. Is that a good idea? Not now when you're trying to get out of the house and into a place of your own (and will have to get out of the house since it's being sold), not when the government is dangling such an interesting offer (and when your income is below the $6,000 cut-off, I assume), and not when you are still wealth challenged. (It seems like you've got basically zero toward retirement, aside from compulsory CPF. Is that correct?)
So, I'd try living on your own (1 year lease probably) and put in for your HDB BTO (2 room Type 2, presumably) when you're eligible (35th birthday). In the meantime, get into a savings habit, and yes, I'd close that insurance gap. I'd also try to scrape together $7K and make that top-up to your parent's SA/RA this month, so you can get some 2018 tax relief for it. And you're probably going to feel miserable doing that, but hey, it's your parent. It just comes with the territory, and that's the best thing you can do both for your parent and for yourself.
I'm keeping an open mind pending more information, but that's my current thinking based on the available information.
How far away are you from age 35 (and HDB eligibility), if you don't mind me asking?