After talking with a few, some of them advised me to send tax documents (I don't what is the right term in English so forgive me about that :)) on my LLC for 2019 and some told me that it's ok not to send because I didn't have any activity on my LLC in 2019...The one that advised me to do send, told me that if I won't send and the IRS will audit me, I could pay a fee of 25,000$!! 

Also, what guarantee can they give you on an audit that tax software cannot?

Finally, you can have water company come out and audit water usage.

Someone who's just general is likely to just cpaitalize it all- and any one who says you can expense a whole $500k renovation is likely to end up getting you audited becuase that's bs. 

Environmental audits and reports.6.

You are also able to click on each lending company through the website and if their is a violation recorded against them from the DRE, the complete report and audit finding is posted to their license profile.CA is a little over the top with their reporting requirements but they do it for a reason.Each state is different.  

So I can obviously lease the office building back to my company for a non-audit triggering amount. 

It goes on the books in 2019 as a sole proprietor... unless it means I get audited?

It is always a good idea to have a contract in place regardless but you should be able to write off the leasing fee but if you get audited you will need to provide proof. 

if yiu get audited just plain it.