劝阻老人不要参与这个项目：

1. 铁皮屋建造商不一定兑现承诺。再严密的合同，公司出问题钱也是拿不回的。
2. Zoning，lot and utility development are questionable, and cost lots more money, and looks builder is not responsible.
3. Building code violation. Never heard here in US people living in such house, even it is vacation home.
4. Maintain such a building in countryside cost money.
5. Help our parents watch out their retirement nest eggs and build up financial safety nest for their golden age is our duty.
6. Instead of warring for them, the best solution is to invest your love and a little money to purchase a home together in countryside
or suburban with ownership. They can enjoy their vacation now. The living conditions will be better as urbanization. When they rent out their city home if needed, their financial future is secured. The reward for you: A true loving daughter and a place you can also call home and a property can pass through generations.
7. May be you can not do this now, put it on your wish list and you will feel good and meaningful.

Thanks for reading