The longer you wait, the more chances there are for problems, which means dollars out of pocket, which means added cost to the REI, and even more of a delay to the profit point. 

It sounds like your cleaner is charging more no matter how many people stay, so I would recommend upping your nightly rate a few dollars to make up the $50. 

However, if I'm just looking at the structure/improvement I believe that a home would depreciate following a curve in the same way that most physical goods depreciate on a curve (in terms of real dollars, adjusted for inflation). 

Every dollar made was put aside and then used to reinvest in another property.

So I made a compromise with myself, instead of putting that $100 directly to my principle, I'm opening a brokerage account that will have $100 deposited into it automatically every month and invested in index funds using dollar cost averaging method.

The lower dollar loans have a very high percentage in closing costs because the cost to underwrite a $500k loan is the same as a $75k loan unfortunately.

As near as historians can figure, Washington’s net worth at the time of his death in current dollars was over $1 billion.  

Thats the million dollar question. 

This works best on used homes where the price is only a few thousand dollars, but if it is a brand new home worth tens of thousands you could offer to help them sell it.

When I have a client who has given me millions of dollars of business and referrals ask for a break if I am a dual agent or if the sale price is in the millions I happily oblige.