I have dealt with this numerous times, but a Realtor is not the person to answer this question. It is possible to get a mortgage/construction loan, but they are rare.
You need to talk to a good lawyer (free consultation)
And a good mortgage broker
I have been in the business over 15 years: I have access to both.
Give me a call... I would be glad to help!
REMAX NEW YORK
261 4th Avenuue, Brooklyn NY 11215