A lot of the beach rentals down there are pretty outdated and don't provide many amenities.

I would highly encourage paying a GC to walk deals out the gate, have them give a scope of work so you can see what items costs.

I have provided them a letter from my broker about the amount that can be used.

If the guest feels slighted, there is no fact checking service provided by AirBnB to confirm their claims, so it is up to you to let future guests know the level of professionalism you provide.If you are able, I would recommend editing your response to the 1-star review.

Our two story more family homes started at 500k and have ended up at 675k to 725k.. with our original nets at 100k ( was the goal) to now we are 100k to 150k NET NET NET on those.. we have 17 more to deliver and 11 are presold at those high numbers and so if I can keep lumber where i need it we should have a very nice last year of the project.

If your house is old, value is low. 

@Matt Smith - as @Christopher S. mentioned you cannot use an ADU unit in Chicago as an AirBNB as the city's intent with the program is to provide additional affordable housing. 

$30k in additional value for $5k invested is a great return.

Is this normal cost or high?

While we see year+ long furnished stays here in the Charlotte area, they are far and few between.With that being said, the furniture, linens, appliances, etc. you provide/leave for guests matters.