What rights do we have?

Location: California (San Diego County)

I’ll try to keep this as simple as possible, so ask any questions if needed. The situation isn’t simple, but the question is, I think.

I(f27) and my mom(f61) live together. The house is owned by my sister (f37?). My mom has been making rent payments for the past few years of an amount she’s able to afford, which is not much, I think about $500 or so. However, in addition, she’s made major purchases for the wellbeing of the house, such as appliances, and even gave my sister $5000 for the downpayment so she could buy the house in the first place. As far as I’m aware, there were no legal documents signed as far as rent/lease/etc. I’m only there due to my moms kindness and not wanting me to live on the street (I’ve been unemployed for 15 months and although I think I’m finally close to getting something, I’m dirt poor and have been doing side work just to afford my essentials and pet care) my presence in the house doesn’t cost my sister anything except maybe negligible utility usage, I’m not home most of the time anyway (side work is often pet sitting). For context, my sister has been MIA and refused to speak to us like a family or have any discussions on her plans besides vague statements on wanting to sell the house someday. She treats our mom like shit also.

The issue is that my sister has suddenly decided she wants to sell the house in less than 60 days from now and expects us to leave the house in “sellable condition” (which my sister herself did not leave it in, and she had multiple randoms living there who were not very respectful of the space). In addition, the house is literally borderline hoarder situation with all of her and my mom’s stuff mixed together (my mom has lived with my sister for the past decade or so). My sister is delusional and thinks that she can just hire movers to take the rest of her stuff out (it’s a disaster) anyway, that’s not relevant to the legality.

I wish I could post screenshots of the “conversation” because that would be easier than trying to explain, but here goes, I’ll try to limit it to only the legally relevant but still provide context so it makes sense.

Feb 24:

- Sister creates a group message with me, my mom, and some unknown number. Sends a message saying she plans to sell in April/May

- she says she “expects it to be in the condition she bought it in” and the “work she asked to get done the last couple of years completed” (for which she never took any initiative to provide input or pay for, so it obviously didn’t get done)

- she accuses me of guilt tripping her when I point out she’s being unreasonable and forming false narratives - I then leave the group chat

March 6:

- Sister creates a new group chat that includes all of the above, plus my dad and his wife (my moms ex husband) (they have nothing to do with this situation so I’m not sure why they’re in the chat except to “intimidate” or embarrass my mom) (shitty, but not illegal I guess)

- sister sends a message listing out our “options” and a timeline for said options. They boil down to: 1. Sort and remove all belongings and “fix any damage” before April 15 2. pay an exorbitant amount in rent 3. Purchase the house

- I laugh at the message because it’s insane she wants $4000/month for a shit ass house in a shit ass part of town (that’s far above market value based on our search for new housing)

- I remind her that the property wasn’t left in sellable or rentable condition, and how disrespectful she’s being by including my moms ex husband and his wife in this chat (they’ve been divorced for like 20 years)

- I leave the chat again

March 7

- my mom sends sister a long but very kind message reminding her that she loves her and is heartbroken that my sister has decided she doesn’t want her in her life, but also reminds her of the things purchased for the house, and that we will require at least 90 days to be able to get out, but again this message is full of love. Very sweet. My sister doesn’t deserve the kindness but hey.

- my sister screenshots that message, adds me back into that chat, and send it there saying it’s “unacceptable” “I don’t owe you anything” “you’re guests not tenants” etc.

- at this point I lose my shit on her and do away with my initial quest to stay respectful and leave emotion out of it, then block her.

My question is, does my mom have rights as a tenant, a squatter, or as a human? I know I don’t as I haven’t paid her anything and don’t plan to, but for my mom, since she’s been paying rent for years, does that not equate to any rights? If she is simply a “guest” can she sue for the rent she’s paid, the appliances, down payment, etc?

Please help us out here, I’m fine if I have to live in my car, I’ll survive probably, but my mom doesn’t deserve this.

Side note, if we do have legal rights, if anyone in SD county knows of any good free/low cost resources we would really appreciate it.

Thank you!!