Make sure each prospect when screening them that your guidelines are understood. 

@Jay Hinrichs, understood.  

Perhaps we should have understood this from our initial conversations with you.

I did all the math by hand to make sure I understood it, then I tried plugging all the same data into the rental calculator on BiggerPockets (fortunately I got the same results in both cases).

I Couldn't find a solid answer I fully understood so was wondering if anyone here knew.

They understood that I was gun shy to enter into a contract because of what I had been experiencing prior.

I did some more research and learned about California's SB9 which from what I understood would make it possible for there to be a duplex in a parcel zoned for SFH.The weird thing is that the duplex appears to have been built a LONG time ago and SB9 was just recently passed.Does that mean the owner had an unpermitted duplex for years and it was recently legalized by the passing of SB9?

Just wanted to make sure I understood exactly what you were saying.I hope this helps and have a great day.

There was a lot of interest in the property and I understood that several offers had been made as I was told as much and saw several people look at the property after I left it. 

Or will it be understood to the seller than I'll be using a HELOC to pay for everything and that should feel like cash to them?