I’ve noticed the larger deals are from brokers and the smaller deals are listed by agents.  

Seems to me that any basic lease should cover renewals, notices, etc...

Our tenants recently told us that, due to personal stuff, they plan to "give 30 days notice"/break lease.

Anyone staying longer than that must submit to a full background check to be added to the lease.If you don't want this guy there, and your lease provides an out, simply state that the boyfriend is not allowed to stay, that if you find that he is staying you will deliver a notice to cure or quit and then follow up if when you discover the boyfriend still there.If you do decide to add him (he's going to be there whether you add him or not) then absolutely do a full background check and credit check.

., is 28 day notice to the landlord really necessary? 

It turns out to be a 3 year violation notice on the property I did not know about when I purchased this property as my primary residence.

Their lease is up in May, with 60-day notice, so it seems like this is something I reconsider in March, armed with this info. 

I can get you set up with MLS auto alerts and I'm wanting to move more into "off market" properties, like divorce, elder and notice of defaults.

The reason I ask is that I have started to notice a few local landlords putting some of their rental properties up for sale, actually a lot. 

You’ll also notice the assessed value is not the taxed value.