Purchasing a property (such as a condo or townhome) that is not built yet is what is referred to as pre-construction. There are many advantages to purchasing during this phase.

Low Deposit Structure

One of the biggest benefits of pre-construction is that you can start with a small deposit (sometimes as low as 5% down) and you don't need to get a mortgage right away. You secure the mortgage when the property is done, which is typically four to five years out.

Because of this financial flexibility, you can rapidly scale a portfolio and add properties in desirable developments.  By deferring the mortgage commitment in the future, you just make a capital commitment now, and then over the next four to five years, you will get to participate in the appreciation of the real estate asset without having to worry about the mortgage side of the equation.

Higher Demand for New

When you buy pre-construction you are buying something brand new and that comes with full Tarion warranty coverage. 

You don't need to worry about any issues in the property because you have the warranty coverage to take care of any deficiencies in the property.

Lastly, your asset will rent faster and for a higher price point than existing resale or older units on the market because people pay a premium and desire properties that are new and untouched.