So I offered to pay for the flight, if they returned a clean and empty house.

I'm more involved with Instagram these days :PI'm currently stuck at the "pick your market" phase. 

If an early buyout opportunity arises, I’m happy to secure a solid return for all involved.

Undoubtedly, the biggest regret is getting involved in the short-term rental market.

I'm in Milwaukee and I have heard of a lot of bad stories involving this type of scenario...mostly involving out of state investors. 

Although the cleaner is probably the most important piece to the puzzle for your STR success, there is alot more involved with managing it.

You must know something about it already, since you got involved in it. 

More like  2X to 5X the cash out.. these are done with builder developers on their deals So put out 300k get 300k back in profit plus the interest rate. most small builders/ developers need to have a equity partner so you just do both you lend the money and are the equity partner.. pretty clean..

Put language in your lease about use of the screen for all fires.I always made it the tenant's responsibility to have the chimney cleaned at least once per year for the built in fireplaces and twice per year for the store bought types as they have smaller chimney piping.  

Build a local team for cleaning and repairs to streamline operations.