Landlord Signed A Lease, Took A Significant Amount Of Money Upfront, And Then Immediately Sold The House. (california)

Okay, so this was a bit of a unique situation, but my brother and I lived in my grandmother's house because we were her full time caretakers during the end of her life. When she died, she didn't leave a will, and my mom was the only other person whose name was on the house. Big mistake, and if my grandmother could ever have foreseen what would happen she would have taken measures to prevent it.

My mother is a severe alcoholic and for the past 5 years or so has been rapidly going insane. She has a severe spending problem (Shopaholic + Compulsive Hoarder) and my stepdad divorced her, and without his income to siphon, her lifestyle is not financially sustainable. She already filed for bankruptcy once, and I presume the past couple years she's just been living off credit cards and racking up debt. I also know she owes the IRS a lot of money because she hasn't been paying her taxes. For years, she has weaponized the fact that the house is in her name to lord over us, forcing us to put up with constant mental and emotional abuse and harassment in order to keep a roof over our heads, and on several occasions has used it to demand an increasing amount of money. Up until now, we were able to negotiate leases that essentially amounted to us paying all the upkeep on the property that she couldn't do in her condition, as the house would have been a derelict and had squatters and all sorts of bad news if we weren't here. We also did a very significant amount of repairs, most of which we paid for parts out of pocket.

Every time we had to get a written lease signed just so she can't change her mind anytime she arbitrarily wakes up in a bad mood and decides we have to be punished for it, or constantly threaten to kick us out,

So our lease was just recently renewed. She was saying she was running out of money and was acting squirrely, so we cautiously agreed to a new lease, in which we increased the amount of rent we were supposed to give her monthly and agreed to pay the semiannual property taxes, which she literally said she didn't even have the money to afford, meaning she needed it paid and would be screwing herself if she kicked us out. We were able to leverage that to get her to sign off on another 6 month lease. She also knows that this house is not up to code to be able to rent out commercially, so as it stands it is the logical decision to rent to us anyway.

So we sign it, and I pay the property taxes upfront, about $1200, which was really money I didn't have, being disabled on a fixed income, but whatever, if it buys us another 6 months then so be it.

Barely a week later, I come to find out she sold the house AFTER already signing a lease with us. I'm out pretty much all the money I had, and she sold the house out from under us.

What exactly are our options here? The lease is somewhat informal and I worry an experienced lawyer might be able to poke holes in it. She sold the house as-is for cash to one of those fly-by-night vultures that have been buying up all the real estate in the area, and I'm not even sure if she mentioned the fact that she had tenants with a lease she just renewed.

Is the new owner required to at least honor our lease until it expires, or is there a chance they're all gonna try and ignore the lease and try to get us out anyway? Do we have any grounds to sue for fraudulently signing a lease and immediately violating it, or at the very least taking her to small claims to recoup the money I put down? Is there any chance we could also sue for the money we spent on repairs and maintenance, if it's even worth pursuing?