Overall, there is probably enough housing in the US for everyone but no one wants to live in Northeast Iowa or Central Mississippi so there's a mismatch between available housing and where people want to live.

I have invested to make the house nicer and added some amenities only to see achievable rents go down from last year.  

It is a lot of traditional sales.Go on the websites of Sirva, Sedgewick, ALE, CRS, and others and submit your housing to them.

I've got a 2nd floor detached garage build i'm in the planning/permitting stages of here and looking for advice to see if any key features need added.It will have its separate entrance from main garage which will be utilized by main house STR for a game room eventually.

I would mention here that a typical condo or single family does not qualify for the Act 60 TOURISM tax credit (which gives you up to 40% back)  - the project needs to meet certain qualifications as a guest house, hotel, villas or bed & breakfast - it can be as little as 3 rooms.  

However, I am wanting to take the abandoned houses and revamp the town.

To give you some background, I'm an investor developer, where we do land development projects typically for multi-family housing. 

Our family are relocating to another state and we want to rent out our house that has a pool.

What are the advantages of doing a BRRRR on an existing property vs. buying the land and building a new house from the ground up? 

what about a prefab sustainable house.