Troubles.
You have to get hookups for utilities.
Worry about construction quality. Durability in a storm.
Architecture. Will the house fall down?
Material quality. Is the wood good?
Electrical wiring. Is it up to code? Will it burn the house down?
Plumbing. A leak can destroy a home.
Mold. Moisture ingress. Bugs. Termites.
Foundational stability. Water drainage.
You can get it all apparently right only to find your home is worthless or can't be lived in after a decade.
All of this is before the regulatory issues, permits, taxes, insurance, and so on.
It's nowhere near as simple as picking up a nail gun.