How practical and expensive would it be to add a story on a ranch style house?

Answer 1

That is often done.
First there are several things to consider.
1. Do the local bylaws permit 2 story houses in your area?
2. Is the frame of the existing house strong enough to support a second story?
3. Is the current heating / cooling system robust enough to meet the needs of the additional square footage?
3. Is there access for heat ducts, electrical wiring and plumbing into the new area?
These are only a few of the considerations that must be considered, then contact two or more contractors for a price to do the Job.

Answer 2

practical, call a contractor and get an estimate,