We incorrectly determined the after repair value, Interest rates quickly increased, and used a fix and flip line of credit with unexpected costs and regulations.

Since no one has chimed in, I'll give my $0.02...I'm not a CPA and I could be 100% incorrect, but my understanding is that, even if you're making estimated payments based on safe harbor, you're still required to be completely paid up on April 15th regardless of whether you're filing then or extending until October.  

B.t.w investor portal sometimes show incorrect info as well.

I Would have waited to see the other hoke close if I had any indication that she had incorrect information. 

Also, should I return the incorrect rent of September or do I hold on to it until I received the full amount?

Hey @Thomas Rodgers- although your approach is unique, I think it's incorrect.

I'm new here, please feel free to school me on any incorrect assumptions I may be making. 

@Logan LehmkuhlAs @Scott E. mentioned, there's a lot of really good information on BP lately for Subject To.Here are some considerations for buying sub to- Subject to can be an awesome strategy BUT if structured incorrectly there could be serious ramifications for both you and the seller.

One question I had when reading: I thought most banks didn’t allow you to be “gifted” the down payment...is that incorrect?

They were first-time buyers and relied upon the listing to justify the price that they paid.I remeasured the house and found that I was incorrect.