Linda Weygant from podcast 244 has either most or all of her properties in HOA's.

But if you ever ran into a situation like health, accident, etc. forcing you to liquidate some or all of your assets, it would be nice to know your end buyers won't have any issues lining up financing.

For all you know, any or all of the roof, plumbing, and electric might need complete overhauls.

do some or all of the above places i mention give cause for concern?  

Or all 4 units have to be put sold together?

Getting rid of most or all of that debt may accelerate your credit repair.But still, keep a little cash on hand, so you can handle an unexpected expense.

Save up enough so that if you buy a place and the roof caves or all your hvac units explode, you have the funds to cover it.

Once the seller put the house on the market, he should have gave a heads up to the tenants that are on month to month that there's a chance that the new owner may want some or all of the tenants out.

And that's new information to the seller, you can improve your negotiation position because they are then required to disclose to future buyers is my understanding.On to the technical and again I'm brainstorming out loud here....I have ZERO experience with mud jacking as a permanent solution to slab heaving issues - however I would wonder about the feasibility of this as a 'roll the dice' kind of solution (good money vs value trade off) ...if you buy.One possible solution may be to jack the house and repour which I don't know much about how the bottom plates/wood structural would be tied into the slab - but jacking the house and re pouring sections or all of slab would be an incredibly costly endeavor. 

Something where the profits from having three units rented carries most or all of the fourth.