How much bargain with builder?

昨天看了一個 brand new townhouse, on the market two years, not sell, the inside not finished, nothing inside, no carpet, no appliance, the owner (I think she is the builders wife) ask $149000, if finish inside, ask $189000. I ask her why this house in the market two years, she told me because they are device.

These townhouses have eight units, two ends sold, and other six on sale now. My questions are

1) How much I can negotiate with builder?
2) How much should I pay to finish inside, does it a hard job DIY?

The location is not bad, good school district, the outside looks not very attractive.

Any suggestion will be very appreciated!!!!!!!!!!!!!