500K+

Yes, agree with 812 up there.

Are either of you able to weigh in this n what the cost would include? We'll be adding on to a standing structure that already has 2bed/2bath.

Maybe you could provide more information.

Do you have any contracting experience?

Are you able to list what you want in detail? That means floor coverings, lights, everything in detail, including paint.

You have to have paid design work done first, that specifies what you want. Then you get dialed in prices on that. But 500K is a rough beginning price in this time frame, in your location. Your location is 35% above the national average. It takes $1.35 to live there, but the national average is $1. But housing is 179% compared to the national average. That translates to construction costs.

You want to add an entire house to a house. With unknown plumbing and electric situations that will likely need to be 100% redone. That's if zoning or setbacks even allow that to happen.

Ask someone local. In the building business. Preferably with your construction drawings in hand.