What if you are in a car accident and get a judgement for a million against you--they could seize your father's house as it is NOT your primary house and he would have nothing. 

(b) In the event sellers refuse to pay, do we have a chance to prevail judgement  and (c) Is it worth fighting this case given the PSA is for a low 7 digit price?

Good on you for not letting emotion and the excitement of getting a deal cloud your judgement. 

I think you can (depending on your state) include a "confession of judgement" clause whereby if he does not stick to the payment plan you can record the IOU as a general lien against him the same as if you went to court. 

@Jay Hinrichs Do you get judgement reports and check the validity of the past transactions? 

Are past years unpaid taxes a lien on all the owners real estate ? We are trying to buy a property and it has previous years unpaid taxes that will be paid at closing. The closer says the sellers taxes on all their ot...

If you don't pay unsecured debt you can get sued and a judgement will be put against you.

Turn your judgement into a lien on the property and keep adding the value of rent, and the expenses and maintenance cost, along with interest due -to judgement each year. 

Once you start clouding your judgement based on personal feelings, I think you've lost.

The recorded liens against the property look to be valued at about 400K.The final judgement of foreclosure is close to 500K.From what I've learned on this site, it’s my understanding that when an IRS lien is put onto a property, that IRS lien becomes the primary lien and the mortgage holder/bank becomes the secondary lien.