Building a new house typically requires more collateral because the bank is wary of loaning the money and then the project falling apart before its finished. When that happens, all they can reposes is parts of a house that aren't even worth (on the open market) the cost of the building materials and work already put into it.
It's not a huge deal if you go with an existing builder with lots of experience, especially if they already have a relationship with the bank... but if you want to save money by being your own general contractor or do any work yourself, that's when you encounter the most problems.
Got a new, half million dollar house. (not sure if this counts)
Got the upgrade on insulation(got it in the attic/garage area). Got the upgrade on the triple pane glass. Nothing, has broken in 2 years.
Since, I've used it to rent out AirBnB, rent for friends, and soon house many children.
It would have been nice to save 100k and get a smaller home, but builders make nice new homes, not smaller lower cost homes.
I would already own a house if there were reasonably sized houses on the market that were well built. But there aren't. There are acres of McMansions springing up everywhere, but no sensible, functional houses.