Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Some years back my ex-wife's parents died and she was left their 20 year old single story ranch house. She sold it to our daughter and son-in-law. They had a 2nd story added and also added AC to the whole house at the same time. Doing such is quite common and cost effective.
If one is handy, they could pay to get the shell done, outside finished, basic plumbing/electrical done then take their time finishing the inside.