Delays of a week or more are common, which is particularly problematic when tenants need essentials like AC or hot water.

Each municipality is going to have different permitting requirements. 

@James McGovern that is pretty sound advice that @Rod Hanks has. 

I'm out-of-state from where the property is.

Quote from @Priscilla Rodriguez: My name is Priscilla Rodriguez, and I’m a former Florida Realtor turned aspiring multifamily investor, currently diving deep into the world of underwriting (and trying not to drown in spreadsheets I’m looking to connect with a commercial or multifamily lender in or near Lake Mary, FL who’s willing to share their underwriting knowledge — someone who doesn’t mind a curious mind and a lot of questions (I promise I bring snacks and good energy).I’m so committed to learning the process the right way that I’m happy to intern or shadow you for free.

Trying to do this long distance is often a recipe for disaster as neighborhoods even a short distance away can hold vastly different property values. 

In that case it is a title issue for your title company and the title insurance.More realistically until something like that is raised I would take a firm stand stay away or there will be legal consequences.  

I will place a list of reasons at the end of this reply, but the biggest is that ADUs add less value than the hands off cost to add the ADU.more work and risk, but far better investment is to attempt to subdivide the lot.  

My full-time job is her.

It is going to be much more detailed and realistic than a spreadsheet in my opinion.