Your question is in the Hamilton Heights category, though your identifying info says you are in Michigan. I am going to assume you are asking about Hamilton Heights in NYC. If that is the case, many of the answers below don't apply because they are not specific to the NYC market which is truly unique.
In NYC if there are not 51% of units in the development sold or in contract, you will not be able to get a mortgage. You can, however, have a signed contract stipulating that when they reach that threshhold, you can close. That is common. Once they hit that thresshold, everyone closes like dominoes.
There are other reasons in NYC why a bank won't lend on a specific building. One is if too many units are rented out and not owner-occupied. Another is if the sponsor has withheld too many units or any other purchaser owns too many units - no individual or entity can own more than 20% of the units.
I conditions truly exist where banks won't lend on a specific building, there are other options. One is a portfoliio loan. This is where the bank keeps the loan in-house and does not re-sell the debt on the secondary market. Your rate will be higher and you may need to deposit substantial assets with that lender.
There is a great variety of terrific buying opportunities in the city right now, so if that particular building is not working for you, there are many other great choices. I suggest you work with an experienced, skilled agent who can streamiline your search, negotiate on your behalf and overcome any obstacles along the way.
Hope this helps.
Halstead Property, LLC
Licensed Real Estate Salesperson