Might be best to just try to pay more each month on the principal or sell the car and buy something in cash.

I agreed to effectively a short sale: mortgagee sold property and I received all proceeds, which did not quite cover the principal amount and thus didn't cover any of the accumulated interest.

Ultimately the sellers ended up accepting the 183k, I put down 10% instead of 20%, since it was my principal residence, not an investment property.

The variable interest rate on the loan is currently 4.5%.So, if I were to draw 50,000 from the HELOC to pay for this rental property, my minimum payment for the first month would be $750, of which about $188 would be interest, and the remaining $562 would go towards the principal.

One alternative may be for your father to take a loan from his retirement account.In order to be able to do so you father would need to be separately self-employed (although not necessarily on a full-time basis as I know that he just retired).Regarding taking a 401k loan: If your father is self-employed with no full-time employees & he could set up a Solo 401k, rollover the funds and take a 401k loan from the Solo 401k.He can borrow up to 50% of the balance not to exceed $50,000.The repayment terms are equal monthly/quarterly payments (as you prefer) of principal and interest (e.g. prime + 1%) spread over a 5 year term (or longer if you will use the loan to purchase your primary residence). 

Since I have been paying extra on the principal amount aggressively and the house value has increased quite a lot, my LTV ratio will be less than 80% with a new appraisal.

3 bed 2 bath 1200 sqft single family Principal Loan: 94k + 15k arrears/taxed&fees = 109kARV: 120k My question is would this be worth a 15k down payment to stop the foreclosure, and use owner financing to possibly rent or sell?

The deceptive part is the principal portion you are also receiving.

However with principal paydown, saving for more units each year, I will reach my goals in time.

From October to December of 2017, they brought in more than $52 million in investor money before filing for Chapter 11 bankruptcy in December 2017.Prosecutors said filing for bankruptcy caused investors to suffer substantial losses on their $1 billion in principal.