If you see an MLS listing that offers a condo “assignment,” this means that the seller isn’t actually selling you a condo, like they would in the resale market. Chances are, the condo isn’t even built yet, or at the very least, the building isn't registered with the city and the owner hasn’t officially closed on the unit.
A Buyer is buying the agreement the seller made with the builder to purchase the condo once it’s ready. This can be a strategy for a relatively quick return. You can think of it like concert tickets. Most big concerts sell-out immediately, but then tickets become available through online re-sellers. In this analogy, the condo is the seat at the concert, and the agreement with the builder is the ticket. Selling on assignment is like selling a ticket to a concert.
Formally, an investor would enter into an agreement with the builder to purchase a unit based off of plans. As the condo building nears completion, due to increases in the market and the readiness of the unit, potential buyers will likely offer more than what was originally signed by the investor.
Most builders won’t allow selling pre-construction condo unit agreements on assignment without their permission, and some will charge a fee for it, ranging in the hundreds to the thousands of dollars. This makes sense, since it entails some added work on their end to be dealing with new people as agreements change hands.