Tax Abatement

Hi. I am seriously considering purchasing a condo in Carroll Gardens whose tax abatement is set to start phasing out (I think that’s the right term) in 2015\. Monthly is currently $150 but it will start going up 20%.
I like this much better than some of the new construction I have seen that is just starting their 421-A abatement but wondering…should a learn to love a brand new building?  Certainly more cost effective.
But I have been at this for a while and I do love this place. But the seller is only so negotiable. Can someone help? I keep finding out more about what I don’t know!