How to make this low offer??

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OK. I have spent the last week mapping out my plan to get started. I have a goal to purchase my first property by the end of August. I have been watching a house that has been for sale by owner for at least 6 months. I called and was able to get permission to access it from owner a few weeks ago. 

It is a 3 bedroom/1 bathroom 50's cape. Nice, rural area about 10 mins from town. New roof, new windows, new vinyl floor. I am accounting $4900 for replacing the heat pump as it is quite old and it needs all appliances. The layout of the bedrooms is funky (probably is really a 2 bedroom originally) as you have to walk through one bedroom to get to another. This can be fixed up better with a few 2x4's and some sheetrock eventually. I can do this.

Anyway, it was previously listed on MLS for 80ish almost 2 years ago. The owner is elderly and living with family now. Has owned it for 50 years. Son is taking the calls and is an inactive, licensed agent. Super nice guy on the phone. Price is now 70K.

I made this spreadsheet and am attaching an image. I'm wanting to explore owner financing (with $7000 down) but also need it at more than a 50% discount to make the numbers work. I'm thinking of writing a letter directly to the owner but am nervous about offering 32K for a 70K asking price AND trying to get owner financing. I understand the worst they can say is no but want to keep the dialog open. I am currently unable to meet them in person as we are traveling for the next 3 months for work. I imagine it will still be there when I get back.

Here are the numbers: https://imgur.com/a/wNJmGng

Thanks everyone for any input.