Subject -To Calculations

[Thomas Lee Malpass]

I need some help calculating a potential Subject-to deal. Here is the info I have so far... Sellers Loan Amount $500,000 They are currently asking $799,000 as the purchase price. 

The property is a multifamily Quadplex currently fully rented at $4200 total with some leases ending soon and rents increasing to $4800 if fully leased out. 

I am still doing due diligence on the PiTi loan payment, but the property was bought in 2020, so I assume they have a decent interest rate.  My question is what else do I need to know to calculate this deal? And if I get it under contract how could i make this deal work out? THank you so much for whoever helps me on this.