For example if I owned a unit for 30 years that's only 360 months, so a vacancy rate pre rent moratoriums of 5% would give me 18 missed months in 30 years.  

I think we're missing some info, as Chad asked.

I think looking at properties that have been on the market for awhile especially can yield opportunities since people will assume something is majorly wrong with the property and ignore it - I know I had those concerns like what am I missing here?

If they can provide a comparative market analysis and help source off-market deals, that would be great asset.I would love to get some recommendations from the experts already in this market.Also, please let me know if I am missing anything.

If you are in a landlord friendly state, that should cover months of missed rent and eviction.

OR one day she will mess up and miss the date! 

Are there any other main expenses that short-term rentals have that I am missing?

Missing most important info. 

Missing flooring pieces, random minor repairs needed.  

I just sold my rental property in AZ and I am thinking to buy a house 400-450K close to the beach and visit 2 times a year.For the rest of the year rented it (AirBnb, VRBO ).Also I am working from home, so potentially I can come and stay for a month or even longer.Is there something I am missing or something negative I need to know in your opinion before I buy ?