400 Park Avenue South is a genuinely well-built building. Toll Brothers delivered on the construction side: finishes are top tier, the curtain wall facade performs as designed, and the LEED certification reflects real engineering attention rather than a marketing label. The amenity program is among the deepest in NoMad: indoor pool, jacuzzi, sauna, steam room, spin studio, yoga room, virtual golf, screening room, and landscaped terrace. Common charges are reasonable given what the building operates, in part because rental residents contribute through optional amenity access fees, which helps offset shared maintenance costs.

The investment case requires eyes-open underwriting on two fronts. First, this building is non-warrantable. Because the condo portion represents less than 50% of total units, conventional Fannie Mae and Freddie Mac financing is not available. The buyer pool at resale shrinks to cash buyers and borrowers with access to private or portfolio financing. Second, the building carries a Grade D energy efficiency rating (Score 42 per Local Law 33, as reported 2025). A Score of 42 is in the middle of the D band and is more typical of buildings in this class than One Madison's near-floor score, but it is worth noting alongside the LEED certification: the building was designed for energy performance, and the operational score suggests room for improvement in how the building is being managed day to day. Together, these two factors, non-warrantable structure and energy grade, are the primary reasons this building scores where it does. The design is irreplaceable. The exit market is constrained. Buyers who understand that dynamic and are purchasing for long-term use or lifestyle fit will find genuine value here.