(Say on the initial purchase if someone is buying right now).3) I can lock in a guaranteed better rate now and enjoy the lower monthly payments now, and only pay maybe 1 or 1.5 points instead of 2-2.5 points later when I have to hope that rates come down again.4) This also saves a lot of time which is an important consideration as some refinances can take 30 days and a lot of paperwork gathering and headache etc.Again, my thoughts on this largely revolve around risk aversion. 

What's your best piece of advice or tip when starting out managing a STR?

Do you require an application and screening before showing the property to save time with tenants that do not qualify?

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.

Maybe the current tenants don't care, but if they are also below market rents and you start bumping their rents, will it be opening the door for more complaints or increased likelihood of them leaving because they are being impacted by the smoker.  

You've been living there for 15 years, and some new rich landlord buys the place and starts raising rents.You need to go on a per unit basis, and address any issues that need repair.

I plan on starting to attend some here as I am sure many local SoCal people invest out of state.

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.

Far too often I see owner trying to save a dime and then a few months later in big trouble because the tenants understand the laws better than they do.

I save on property management fees, maintain control over tenant relations, and personally ensure things are done right.