I think relatively little of it. You can only take advantage of the low interest phase if you operate with high repayment rates and short terms, otherwise you pay a low percentage - but that over a long time on a high principal amount. If, in addition, the land price does not develop as expected/desire, you will quickly lose out, because there are also additional costs for the purchase (notary/property transfer tax) and ongoing costs for the land: property tax, maintenance.
Moreover, you bind yourself to a piece of land that you don’t know if you will still like in 10 years - who really knows where they will be in 10 years? The direct benefit only comes to you after 10 years from the land, whereby that is exactly the value you secure with the purchase if the land itself is not supposed to be the investment.
Research energy conferences on the Internet. From 2021 onwards, the passive house will become mandatory. 140,000 is already absolutely unrealistic today. From 2021 it will rather be more expensive. Better calculate with 240,000 so that you can also pay for a kitchen, paved driveway, terrace, house connections, earth excavation, etc.
