How much should this extra room cost?

[Stephen Shelton]

I know I know I'm cringing at the topic of this, but I'm going to get specific so it doesn't seem so noobish 😄

It's Florida. I bought a single story rectangular block home on a concrete foundation. A back porch was added and turned into 2 simple interior rooms built from wood. The house was abandoned for a decade and the addition was left to rot. Literally.  The floor is even wood.

I want to rebuild the space into 2 rooms. How much (ballpark) should I expect to pay for this scenario:

* Size 30' x 12'  / 360 sqft

* Walls: standard 8'

* Walls: Prefer block, but due to existing structure contactor recommended wood walls with hardiboard exterior siding.

* Concrete foundation

* One basic 6" sliding glass door

* 1 window

* No closets

* No plumbing/water

* No roof (it exists and is perfect)

* HVAC already routed

* 3 total ceiling light fixture boxes

The existing walls and rotten flooring and fireplace will need demo'd and hauled away. The existing walls are loaded with old awning-style windows.

Things I don't want factored into this estimate:

* Finishes: tile, baseboard, paint, etc.  I will do that myself.

* AC: the extra space will likely impact ac system demands.

I do have an estimate on the way, but can someone give me a ballpark estimate on what they'd expect this estimate to cost? I really have little idea.