Buying pre-selling properties be it house and lot or condo during its pre-selling period has a set of advantages and disadvantages especially for first time buyers. During the pre-selling stage, properties are usually cheaper as developers tend to give a discount ranging from 10% to 15%. Keep in mind that as the property gets completed, the prices also tend to get higher.
For houses, the more phases of construction is built the price go higher. Same goes for condos where the price gets higher as more floors are completed or for low/mid rise projects, the more buildings are completed.
When buying a property pre-selling or not, keep in mind the location, location, location. You may also want to do a background check on the reputation of the project developer.