Are they many traditional Chinese courtyard houses in Taipei/Taiwan? Would there be any restrictions on foreigners buying and renovating? Just an idea as itn would be a great project.
Not in Taipei. There are more in southern Taiwan.
In general, a foreigner can buy land in Taiwan if a Taiwanese can buy land in the foreigner’s country. There are restrictions on buying farmland, so you would be limited to traditional houses in cities and towns. You would also need to find a seller who is willing to sell and who an actually sell. Many of these properties have very complex ownership and families that still have them generally want to keep them.
You might look for a si or san heyuan that is going to be torn down, buy it and have it moved to another piece of land. A friend alerted me to one such sale a couple years back but it would be gone by now.
How hard would it be to build one?
I think pricey. There is only one kiln for example in all Taiwan that makes the roof tiles.
There are some here and there around New Taipei and even within a scooter or bus ride but hard to find and not really available. Farther south you go will see more and cheaper. I looked at one in Chiayi Country far from any major roads or public transport. Less than $1M.
They are mostly old and need renovation. No insulation, not wired and very good plumbing or kitchen. Toilet sometimes an add on later. Some have been remodeled.
I’ve been admiring one new Sanheyuan while driving just outside of Shuangxi on Shuangguan Road. It’s on the left just near the corner where you turn towards the High School. So new ones can be built.