Waterfront development Bridgewater Quay will be completed at the end of August - and all 20 apartments have already been sold.
Developer Jon Hay said the majority of the units on Taupō Quay had been bought by Whanganui locals, all of whom would be moving in a month after the apartments were finished.
"It was a more challenging sell in the beginning of the project, because people had to put a lot of faith in what we were saying," Hay said.
"They had to have the vision.
"A number of them couldn't grasp it and didn't proceed, but now they wish they had.
"Those that signed up early on are pretty happy, I think."
The apartments come in various sizes, with some facing the Whanganui River and some facing Taupō Quay.
"The original building was fantastic, and we've tried to honour that as we've gone along," Hay said.
"There are 38 people on site at the moment, from all around the world.
"A lot of the labourers are local, and some of them have been with us since the day we started.
"They've done a fantastic job. We couldn't have got there without them."
Hay said there was a chance that stage two of the project - involving the acre of land next door - would be placed in the hands of somebody else.
It is currently occupied by the former Whanganui Chronicle printing factory, but that could be demolished to make way for six individual lots.
"You could buy a plot of land and do what you want, six times," Hay said.
"Another option could involve parking and retail on the ground, then three levels of apartments, and a couple of penthouses on top.
"I think that's the way Whanganui will go in time.
"We've got over 300 people in our database that want to have this type of accommodation in Whanganui, so there's definitely a demand."
Whanganui had been "really flat" for around 15 years, Hay said.
"In some ways that was good, because a lot of sh** developments didn't take place here.
"The next generation of millennial developers are really about quality, so Whanganui is going to be the beneficiary of that, especially along the waterfront.
"I think between here and the [Cobham] bridge, that's where people will live in 50 years' time."
In days gone by, everything had been built "backwards to the river" to allow for rubbish to be washed out to sea, Hay said.
"At the moment it's just concrete works and container storage.
"That's all changing now, especially with things like the beautiful boardwalk. You can walk from here to Castlecliff."
Property Brokers Whanganui branch manager Ritesh Verma said apartment-style living was "pretty normal" in other New Zealand centres, and it would only increase in Whanganui as more people moved to the city.
"In Whanganui, we go down Victoria Ave from roundabout to roundabout until we get a park right outside the shop," Verma said.
"It's just a mindset change.
"Imagine if you've got another 100-odd people living right in town, they'll go for a walk on a Tuesday night and have a wine and a meal.
"That increases the vibe within a city."