Building a plane in my garage. You'd be surprised how minimal yet how strong a lot of these structures are. The vast majority of the material I use is thinner than a credit card.
It sounds like it would be a great project.
Thanks.
Hard: I took a class from a licensed A&P mechanic and while not mandatory, gave me a pretty good idea of what I'd be up against. It is extremely challenging even with a kit however. Lots of learning, lots of redoing stuff because of mistakes, many many hours.
Cost: whatever you want it to be really. You can do safe builds probably from around 40-50k for something like a Sonex or Kitfox to several hundred thousand for a Velocity twin or even something turbine powered.
Transport: most people build in their garage and leave the wings off then stick it in a trailer or U-Haul to complete final assembly at a hangar. It's mostly a non-issue.
https://www.youtube.com/watch?v=iPJgm7qP3FY
dramatically simpler than an RV-8. My -8A flying cost was about $75K a decade ago, it would probably take at least $90K today. An S-21 would probably be more.
Some kits come with a folding wing option, so they can be trailered.
The primary decider in the difficulty/time factor is community and your Technical Counseler [1] (usually a multi-kit builder and FAA approved). If you’re able to build near a very active community (Livermore has a lot of RVs), these people will show up at your house/hangar and get/keep you going. Amazing people who can teach you a lot.
1. https://www.eaa.org/eaa/aircraft-building/volunteer-assistan...