@Ian Linayao
Where is your wife on all of this? If you were my investor I'd advise you to hold a fairly hard line in getting an agreement signed. Language barriers and outbursts don't help anyone, and are definitely a point of control. If your wife can be pressured by her father, and her father is living the "Happy wife, happy life" conundrum you could be in real trouble.
The rental contract should protect everyone including the tenants. I've never read a California Association of Realtors Lease for Residential Property, but I'm quite familiar with Georgia's...both states are a part of the National Assoc. of Realtor, at least I know GA is. In a GAR lease it lays out what happens if the tenant is late, or doesn't pay rent. What happens if there's damage. Who's responsible for what, both tenant and landlord. What will happen if each side breaks the lease, and who get's what, and in what time frame. Bounced checks, dispossessory, the works. It's all there.
If this breakdown in communication is going to be you pointing out that the lease clearly says the tenants are responsible for X, and then people start flipping out the you should really consider moving on.
The most common thing I say on a daily basis "What does the lease say?" It's black and white, and as many issues as you can see that way the better you'll be.
Get them to sign a strict lease setting expectations. If they won't, 60 days notice, and start the party.
Disclaimer: Georgia has been open and reopening from the pandemic for over a year, I have absolutely no idea where Cali is in this whole can't evict thing, and I do know you're about the most tenant friendly state there is. So perhaps you just skip over all my Georgia stuff and I just say that I'm rooting for ya to get something signed.
Best, man. GL.