If you build "agile," you have to be able to afford it, or you will go under hopelessly. Since you obviously have to take out money
must, you cannot afford an agile approach (--> we solve the challenge when it comes and remain flexible in planning and adjustment), because very quickly the project will become six digits more expensive than originally thought. You have to be able to smile about that, then it’s really fun.
Since this approach does not seem appropriate for you: Make yourself the most complete list possible of the "subprojects" to be tackled. You can compare this list here. Include all suggestions in the list, mark those that are not so relevant for you as "rejected." It’s a mnemonic aid and "checked off" relieves the mind.
What makes building "surprisingly expensive"?
[*]Forgotten necessary expenses
[*]Spontaneous changes of details during the construction phase
[*]Consistent calculation with the "cheapest" options
[*]Bad construction partners
[*]Overestimation of own contribution
[*]"Champagne taste" but "beer wallet"