I don't know why her father didn't leave her money to pay the taxes

I used Design Appruv on my first ADU and they have since gone bankrupt and stole everyone's money :/...so don't use them, but do look up their Yelp reviews if you want a good chuckle.My buddy CJ just left ADU Geeks and is starting his own company - I think for quite a significant discount. 

For my money and having had a number of properties there I think that FL is too boom/bust.

Roll it into the rent with a lease clause that anything over $X is split 50/50 between both tenants and you don't care who uses more water...In short, spend some money and make it a legal duplex or at least make it two separate units.

I was talking to an investor who told me if he bought my property, he would borrow money from a hard money lender for a few months and then refinance with a regular lender. 

Lawyers are also motivated by making money and I've seen some investors set up ridiculously complex structures. 

If it was a Class A property and you had to make it really nice in order to fetch premium rent, I could see spending money on it.

If you bought a 2-family and started renting both sides, when one tenant leaves, you could choose to move in and then house hack and refinance at that time and get money out and buy a second property.

All this has been built into the loan along with operational cost to get the place running.

You're being a bit short sighted in a long-term game. $200/month net cash flow today is an 8% CoC return in the scenario you described.