250k usd in bank account to open business

No, you can hold max 99% (and lose a 100%) and in theory not need any capital (by law). That is, where the theory ends, as each city/province have their FDI plans and each wants to better than the other.

Therefore you will get very likely get asked to proof your capital (quite common USD 4000 +, never seen below) depending on a massive number of factors including  location, business sectors, corporation form, licences needed ... .

There are dozens of topics to that here in the forum to that matter.

And yes, 250k is not the highest asking price I know. Multiples of that are also quite common.

Many times, it is even useful, to open the business on a different location (more favorable conditions, lower prices) and later move the business to desired location.

Yup.  I personally would not bring that much cash into Vietnam, especially in this economic condition.  If something goes sour, it will be a pain trying to get the remainder of it out, if any is left. 

And yeah, start in a place and among the people you are most confortable with.  Then, once you get your bearing, move the business to a more desirable location.