If you’re buying for rental income or you need to use the property and you have the ready cash, go buy a ready-for-occupancy unit. This way you can immediately rent it out and enjoy the fruits of your investment. RFO types of properties require big cash out. Note that aside from the funds you need to pay the unit, you would also need funds for the fit-out of your unit plus other miscellaneous expenses. Also, it will be best to find a property at a good price. If you have cash on hand that you can use to pay in full, the better chances that you can get a good deal with a property seller.
Now if you do not have a big amount of cash on hand and if you do not intend to use the unit any time soon, it is best to buy pre-selling. Pre-selling units, especially those direct inventories of developers offer low and flexible payment for the equity. As low as 10% equity payable on installment basis, and others have equities payable up to 60-72 months. On top of that, a preselling unit appreciates in value over time where most properties double in price upon turnover.
Again, check your finances and your investment goals. You may also get the services of a licensed broker to guide and help you in your real estate investment. All the best to you!