Dad Bought A Tenant-occupied Home Without Due Diligence Within 3 Days Of Viewing

Context: My dad has been making some increasingly erratic and questionable decisions since my mom passed away 3 years ago. In general, my sister and I (both 30+) are letting him do his thing, since 1-2 attempted interventions didn't go over very well. But, with this latest stunt, we're really concerned that he's getting way in over his head (or was scammed). We're happy to hire a lawyer or whoever to look into it, but I don't even know where to begin, so looking for some advice on questions to ask / type of lawyer to look for / what kind of legal liabilities we should know about.

The story: My dad mentioned a week ago that he's decided (after much pressure from his new wife) to buy a house to stop wasting rent money. He's been living in LA, but decided to look in Las Vegas (due to the favorable tax laws there for retirees). When we were speaking on the phone yesterday about something unrelated, I asked how the house hunt was going. That was when he revealed that he'd already found a place a few days ago - and he transferred the full amount in cash already to an escrow account, and the deed had already been transferred under his name.

When I asked how he managed to do all the due diligence and get insurance sorted (and get a lawyer to look over the papers) within 3 days, he revealed that he hadn't done any of that - "It's not necessary when you buy a home that's for sale by owner! Plus, I agreed to buy this house as is so I don't need to know about any issues with it.").

Upon some further poking to ask when he plans to move in, he revealed that the house is a duplex that currently has 8 tenants, so he can't move in for the time being. He hasn't met any of the tenants, hasn't reviewed any of the lease contracts (the previous owner refused to show them to him without the deed transfer being completed), and doesn't know anything about the tenancies or how the previous landlord managed the property (nor had he heard of anything like landlord insurance before and hadn't been planning on buying any, since he figured rental insurance held by the tenants would cover any issues).

At this point, my sister and I are really worried that he could (a) have been potentially scammed; (b) be screwed over if there's some serious structural issues or zoning violations with the house that he'll need to pay to fix; or (c) be sued or fined if he doesn't meet his obligations to the tenants in any way. I'm not sure where to begin with deciphering this mess, let alone figuring out what to do, though, so any thoughts would be amazing.

tldr; Dad bought a tenant-occupied duplex in Las Vegas but hasn't done any of the due diligence - what should we be worried about, and what would you do if you were me?