I've never seen an automated system that's good at pulling comps and determining an accurate ARV.

You could have an automated email service saying your temporary code will be xxxx for xx/xx/14 to xx/xx/14 once the code is deleted it reverts back to default preprogramed codes (factory set).Do you currently plan to have the unit listed on vacation rental websites or how did you plan to market it as a vacation rental?

Underwriting for single family homes with good credit can already be automated, legal is what holds it up.  

C was smart enough to use the automated system for my lender to request payoff statements (how he figured out the lender I will never know).

Here is the sad story of another ambitious (or maybe reckless is a better word) start-up attempting to automate bookkeeping and predictably falling on their faces.

Now, between my channel manager, cleaning team, and maintenance team, the process is nearly fully automated.

@Gerry Magrini - Hi Gerry, as others have noted there are a lot of good tools out there that could be worth considering; but definitely look for a software solution built for DIY landlords (1 - 15 units) so you can bring some sense of automation to the rental management process (just to make things much much easier for you). 

And do you recommend any specific calendar integration/ automated messaging systems?

A little about myself, I have an extensive IT background, very familiar with systems and business process automation.   

I am automating my new website now.