I can't prove he is, she can't prove he's not.

You have to prove that there was a valid contract (many wholesaler's contracts will not bear scrutiny), that the defendent was aware of the contract, that he acted improperly, and that you were damaged.You also have to do this all in a way that doesn't bring down the authorities on your head for brokering without a license.And without specific performance, all you get is your actual damages.  

If you are a new agent possibly but if your experienced and can prove your good then not so much but you would need to be able to market yourself very well.  

Growing in this way also proves your track record to lenders and potential investors.I had a financial adviser who always advised me to risk a little to learn before I go all in, or at least go big on something.  

Obviously proving that he is spending the night is difficult without video inside the house. 

Studying some property here in my area.

My partner and I are differing on which way to do the layout.From my studies, a true 1 bedroom would maximize our rental income.However she believes we should make it all open with a little staircase that leads up to a small bed.

Suggest you study with the objective to have as much or more expertise on Anaheim rentals as your real estate agent.

I would only post notice if I could prove without a shadow of a doubt in a court of law that the tenant willfully and knowingly did a modification that I strictly forebid.

Based resources to study: Jay Abraham, Rich Scheffren, Dan Kennedy, Perry Marshsll, to name but a few.