The only part of your equation you might want to reconsider is that you can, generally, buy a flying Kitfox for less than you'd invest if you build your own. You can still perform your own maintenance although how you go about it varies depending on its certification category (EAB, ELSA, SLSA). You may need an A&P mechanic to sign off your work though.

Build if you enjoy building and want to get the exact configuration that suits you. You just won't save money going that route and it will take some time.