I started writing because the same questions kept coming up, and because the answers people were finding online were either too generic to be useful or written to sell something. The gap was not information. The gap was someone willing to sit down and go through the numbers for a specific household.
So that is what this site is: the explanations I would give you in a first conversation, written down properly, with the reasoning shown rather than the conclusion asserted.
What I have learned from sitting with homeowners is that the expensive mistakes are rarely about choosing the wrong property. They are about starting the process in the wrong order — falling for a unit first, then working backwards to see whether the numbers can be made to fit.