Building at another location: Where are the lawyer and the construction expert?

In my opinion, the lawyer needs to be familiar less with the state building regulations (that is an architect’s issue) and more with contract law for work and purchase agreements. I wouldn’t make a big fuss about it, but simply have the contract checked online (i.e., by mail or e-mail) (this also works with "real" lawyers, they just don’t have to be located around the corner). By the way, I believe that usually only one contact will be necessary (contract review). Afterwards, you only need the lawyer in case of a dispute, which does not occur that often. And then you can also choose another lawyer locally.

Ideally, you choose the expert so that he can be on site very frequently and at short notice. In my humble opinion, this is less a cost issue than a time issue. For ours, the construction site was practically on the way, so that he was on site up to 10 times a week during important phases (morning, afternoon). This is certainly a fortunate special case, but I would aim for such a constellation.