Yvonne, you are absolutely right. With good wooden windows, upgrading to triple glazing is relatively affordable, but it is not a must. I see the water pipes more as a must. And new seals on windows would be peanuts. Regarding the TE. If there are tiling works, if floors need to be redone, and you have everything done, it will be expensive. Then the 50 will never be enough. It might not be the 300 of a public renovation project. But if you have no idea, planning is difficult without an architect or engineer. Then you need craftsmen you can trust. Please consider together with a professional whether this business is your thing or if you are the wrong person for it. Karsten