I agree with that. In any case, avoid applying for separate financing for the purchase of the land and later for the house construction! Otherwise, you put yourself into an unnecessary dependency on the bank that financed the land, as they then block the land register.
With a financing amount planned by you of 285,000 EUR, you are looking at a monthly rate of about 1,260 EUR, which is already above the desired 1,000 EUR. Operating additional costs will be added.
In addition, the financing will lead to noticeable changes in your previous standard of living (rent previously 650 EUR; new rate 1,600-1,700 EUR!). But if that is okay for you, there is basically nothing against it.
You should also factor in the risk with the employer (even if that is difficult to estimate).
Best regards M. Thiemann