Depending on what type condo your considering and where it is located and your knowledge of the condo and local market and your knowledge of real estate transactions and processes are the factors to be evaluated in determining if you need representation.
Pre-construction condo sales are Extremely Dangerous in most areas at this time, particularly in todays high default rate on condos. In my area three very different prices exist, the builders price which is often something like $850,000, the MLS market value of the exact same type unit in same complex, $620,000 and the distress sale market at $399,900. Those are the EXACT figures on one condo complex in my area.
If you don't know the market you could and many people do pay $450,000 to much for a duplicate unit.
Not only did they Over Pay, they frequently received poor terms and conditions and had to pay extra cost such additional closing cost and possibly your agent's commission. What the builder is probably hoping for, it that you will be foolish enough to just "trust him".
Buying anything with out adequate knowledge is dangerous and buying real estate particularly condos is very dangerous in many locations at this time.... even more so if your being told it is a "good investment".