Why would you build it out of block?
A whole lot harder to insulate, wire, and make it look good enough someone would want to rent it.
For anyone to even guess there going to need to see a blueprint, size of the block (not just 6" wide), and the heights of the walls.
If you Google "concrete block estimator" lots of sites come up.
When posting in forums, letting us know your location will help others give better feedback/advice/solutions to your questions
The Following User Says Thank You to joecaption For This Useful Post: