It is more difficult to sell occupied units, however they often sell for more because they're usually existing. If they have 75 units remaining for example, it would be quite easy to rent 50, and sell the 25, and as rentals become vacant naturally they can simply not find a new tenant as they sell the units. Additionally because this is built after 2018, they could just raise the rents by an insane amount to get tenants out of they desire (not that I condone that, but there's nothing stopping them).
Emblem appears to have deep pockets as well, so I don't think financing is difficult for them. Many other developers would go, and have gone bankrupt after the ongoing condo crash and this far into a project, so the fact that they're starting *another* project tells me they're not struggling financially.