At present, the lot is vacant: https://www.google.com/maps/search/731+bergen+brooklyn/data=!4m2!2m1!4b1?hl=en
In about a year or so, it will look something like this:
"The two 40-foot-tall buildings have nearly identical plans. 733 Bergen will hold seven units spread across 10,546 square feet, producing an average apartment of 1,500 square feet. No. 731 will contain eight apartments and the same square footage, which means that units will be a slightly smaller 1,318 square feet each.
The development will undoubtedly become condos. And if Brookland’s pricing next door is any indication, these units will ask more than $1,300,000 a pop, or somewhere north of $1,000 per square foot."
The above text and photo is from: http://newyorkyimby.com/2015/08/revealed-731-bergen-street-prospect-heights-condos.html
731 Bergen Street
733 Bergen Street