Human error and hopefully it wont cost you any money.

It truly is as the Oracle of Omaha warned, the greatest transference of wealth in human history.

The greatest value for many citizen's is COMMUNITY, and the feeling of coming home, feeling safe, genuine human connection, and self discovery/improvement.

In terms of a PMS system they are all pretty much designed to be fully functional these days, but most are better than pen and paper or simple excel spreadsheet that can have heavy human error attached.

Do you have a habitat for humanity restore nearby? 

LTR STR this is a business and you have to deal with issues and put systems in place. 50% of all humans that buy a rental property sell it in the first year.

I've heard a few national stories over the years, but they were always obvious cases of slumlords, Landlords forcing tenants to have sex with them, or other egregious violations of human decency and law.

If they are good tenants and you to keep them, but on the other hand you still wanna raise, then you're doing the right thing. ..I would tell them that you really wanted to raise them $200 at once, but since you wanna be nice and give them opportunity to adjust their budget, you'll do it throughout the next 2 years.I do understand that is a "business", but I strongly believe that success comes along with the way you deal with people, and even though they are tenants, they are still human beings with feelings just like you, ans a $200 raise at once can get "any" person on your wrong side, and showing them that you're not All about Money and you're trying to respect their pocket will make then do the same and respect your pocket when it comea to paying rent on time etc.

It has more body and you can spread that stuff a bit thicker.

You've just got to run comps yourself as an intelligent human.