I know that certified mail is nesc for official notices like lease renewal, rent increase, notice about bad behavior etc but what about day to day stuff like repairs?

Would you walk away from this deal if the tenant was a bad tenant?

It doesn't matter - You as the big bad rich landlord have a target on your back and will be named to the lawsuit and your insurance carrier will rush to settle it quickly and then you'll be dealing with the long term challenges of having that claim in your insurance history. 

Bad tenants are much worse than vacant properties.I wrote a piece a while back with some other tips you might find helpful too: https://www.biggerpockets.com/blog/2015-05-25-5-dominate-pro...

In my opinion you can't fail unless you don't screen tenants correctly, buy in a bad neighborhood, or get over your head with a rehab.

Is it a bad idea to rent out my childhood home for the time being?

We would treat this like a code violation for parking on the grass or having trash out front.

No fear of the Big bad IRS wolf coming knocking for a pair trail? 

I am not saying LLC's are bad or real estate investors shouldn't own real estate in an LLC.

What I will not do is pay a bad tenant to leave so that another landlord gets stuck with having to deal with a bad tenant that I have rewarded for their poor behavior.