There are a number of all-encompassing software solutions out there, of which my suggestion would vary based on the size of your portfolio and the needs of your specific business.

The direct booking software I use is also a channel manager, so it updates both VRBO & AirBnB.  

It appears to have a higher likelyhood of success than starting a Software-as-a-Service business (I'm a software engineer).

@Bob LangworthyDepending on how many units you have I would spend a few dollars a month and get one of the many PM softwares available.

I was wondering if anyone has a recommendation for the best SMS software for texting campaigns?

@Danny Sharp why use a spreadsheet when there are so many great property management softwares on the market?

Sure, I spent thousands of dollars getting an education for trading stocks, purchased every book I could find, wrote a book myself, developed a sophisticate software for analysis and spend $30,000+ going to classes taught by so-called experts who are only liars and they don't have a clue regarding how to invest wisely and safely.

After you acquire more units tracking on Excel becomes cumbersome and you'll want to transition to Quickbooks or some other real estate related accounting software. 

Which property management software do you use?

Do you use any software to look up their addresses and phone numbers for the owners?