The plot of land appears financeable. The subsequent house construction is to be finally calculated only afterwards. If both economically belong to a common residential project, you must nevertheless assess the initial commitment of capital on the overall project. A promise for the purchase of the land does not automatically confirm the money for the later construction.
Define the entire project scope
Record the plot, construction and all other payments required for your specific scope. Open technical or legal prerequisites will be clarified by specialists. This page does not assess buildability nor a specific construction contract.
For the financing comparison, rough estimates receive a different status than confirmed offers. A house scope that has not yet been reliably defined is not a finished cost basis. You may form variants, but you must keep their limits visible.
Reintegrate a hypothetical partial financing into the whole
In the example for learning, the already fully delineated land requirement amounts to 100.000 euros. For the remaining assumed construction scope a further 300.000 euros are needed. The overall project therefore requires 400.000 euros. Actually usable own funds amount to 50.000 euros; as the total possible loan sum only 280.000 euros is assumed for the case. 70.000 euros are missing.
For the land alone 80,000 euros of loan and 20.000 euros of own funds could initially suffice. However, 80,000 euros of the total assumed loan capacity and 20.000 euros of own funds would then already be used. For the remaining construction there would be 200.000 euros of loan and 30.000 euros of own funds left, together 230.000 euros. Compared with the 300.000 euro requirement the same gap of 70.000 euros still exists.
Do not count an unconfirmed future commitment twice
The later financing must not again be set at the full 280.000-euro sum if the land loan is already included in it. Whether further funds would actually be possible must be examined and confirmed concretely. The example does not set a bank-internal credit limit.
Also ask which costs holding the plot during a delay would trigger and how long this phase could be financed at all. A possible later sale of the plot would be a separate route with an uncertain return, not a secure reversal of the initial step.
Consciously decide the first commitment
Before the purchase it should be comprehensible whether the entire desired residential project is sustainably financeable or which concretely altered scope is to be pursued. A construction plan that is still merely open does not always make the purchase of the plot wrong. However, it does represent an independent capital decision with an openly stated dependency.