my condolences on your recent lost.there are a few ways you can do this, as mentioned above you can take a heloc on your primary residence which will give you a second mortgage, first mortgage payment wont be impacted. you can do cash out refinance which will give you one mortgage and payment. it will pay the old mortgage and give you money in your pocket to pay for the rehab.or you can do a renovation refinance which is similar to cash out refinance but we would contractor involved  as part of the refinancing and they are paid through the loan

Time overcomes low cash flow to some degree... rents go up while your mortgage stays the same and your tenant pays down your mortgage.  

Have a 27k mortgage balance, sale price est at 415k.

If a seller refinanced a house at around 220k and has about 120k left in mortgage, but the house also appreciated to 450k, how do I structure a subto/seller finance deal?

My endgame is to end up with $300k/yr in post-mortgage income in 20 years based on investments I make now followed by continued investments over the next 10-15 years own.

I’d also recommend getting a few quotes, including at least one from a mortgage broker.  

Mortgage lenders will qualify you for a higher purchase amount for multis than they would on a single, because they will count the rent you will be making on the other units as additional qualifying income for your loan application.

I dept free minus these mortgages.  

If you are considering buying using Subject To - Subto, it's important to know what your exit strategy is.Talk to a mortgage broker (not a bank) and ask if that is a property you will be able to get financing on in the event you have to refinance quickly, because the Due On Sale clause was called.AndTalk to a real estate agent about how much you would have to bring to closing in the event you had to sell quickly.

. $40-$50k out of pocket, HELOC or private money loan for the remaining $20-$30k