multi family purchase / development deal

[Caleb Briocher]

I have a deal I'm looking at my lender brought to me that is a 3 family property in Boston with a plot of land that's buildable for me to develop another multi family building on .The seller is asking 1.4 for the deal, I would have to put 20% down for the acquisition at 5% interest. If I was to just sit on the land and not move forward with the development right away I would be looking at a 2.44% coc/roi due to the acquisition of both the land and the property which isn't ideal. But if I was to move right away on the development and get it sold there is a potential to make all my capital back I put down for the acquisition and keep the 3 family essentially having no money tied into it leaving me with 100% coc/roi on the rental income. I'm looking for some advice on if this is a no brainer deal or does it seem like I'm taking a big risk?