I've always gotten the "feeling" that they are trying to do the right thing.1 or 2 clients having an issue with a builder is understandable. 15 is at best, professional negligence.

You can do this on foreclose properties without an appraisal.

That said, figuring out if and what to outsource is important to make sure you're spending your time doing high impact work..

Things that you can do or have access to that not everyone does.

I could do it but why?

welcome. it can be profitable but do your due diligence. network with people that are doing it and try to see if can find mentor.

On the other hand, if you are looking to do a more heavy value-add with renovation you may look for bridge or private money options.

A hands-off garage conversion ADU is over $100, even doing much of the work yourself, it will be much more expensive than your estimate.Single ADU additions in single family zoned areas are typically one of the worse re investments. 

I would do between 50-100% or original deposit amount. 

Start with why you want to do this.