What are the costs involved beside expanding your home? Start with a small smallholding house... then utter we want to knock...

Start with a small smallholding house... then utter we want to knock out a wall and expand by adding an further bedroom and expand one bathroom... impossible to know the exact cost I know... but what are the higher priced aspects of a project approaching this?
I understand purchasing contemporary items for the bathroom, and painting, etc. What I don't make out is the cost of lumber, drywall, etc.
Thanks!
Answers:    Here are some ball park numbers, they are undependable on size of addition, and your location. All sq footage is on the floor nouns.

It is possible to do an addition for $85 sq. ft. Difficult and cheap
For your go up I would consider $130 sq ft for the bedroom and
$230 for the bath. The hip bath could easily be $5000-$8000 depending on what you want. I typically work on multi million dollar homes that budge as high as $900 sq. ft.

I assume no underground store, single story, rectangular rooms with not too heaps windows.

Any time you budget for a remodel impart yourself a 20% buffer in your budget. There are other cost overruns, delays and you might only just want to change your mind sector way into it.

Get a licensed contractor and specify adjectives items for a scope of work. Everything is surrounded by the details.

Good Luck.
Call up one of those places like Lowe's or home depot. They can give a hand you.