You may be able to lean on the title company if they missed something, but generally if the deal closed and its not an issue of material disclosure or title or something its generally your issue now, the owner doesn't really have an obligation to comply if they closed according to the CD you signed.  

There are a lot of charlatans and 'Guru's' out there promoting this and that but the Stech family is the real deal when it comes to Private Lending. 

Price out as much as you can in terms of materials and estimates.

As others have stated, your fit & finish goals should be guided by whether you plan to:1) Rent: tenants don't always take care of a property, so you want to use lower-grade materials and workmanship.2) Flip: higher quality on workmanship and materials is usually required.Regardless, you always want to "Maintain to the Neighborhood".

However, for building materials, we get 99% of them from the four mentioned!

I didn't use it, but I looked at the marketing materials.

Unfortunately the people who promote them do a great job of selling the dream of high returns for zero effort.

I've read a lot of bad information on how some gurus are promoting techniques that are flawed at best, fraud at worst.

You can also promote it on STR outlets (or your agent should).

Estimated CostsADU costs can range DRAMATICALLY depending on the state of the lot, custom vs fast track plans, size of ADU, materials and finishes, speed and quality of the builder, etc.