At inception there is usually an option fee paid buy the buyer, which is not refundable.  

Overseas investors you have extra cash flow withholding.If I was a seller the only way I would take a chance on something like this is if the buyer wires in non-refundable EM from the start and they were paying a below market cap rate for the property.

I am able to command higher rents and have found that the extra rent I bring in during the warmer months offsets the higher costs in the winter.

All other documents are pretty much standard and I can usually work with whatever the title company or borrower wants to use.

Using "the cash flow to pay down their respective mortgages" will be VERY slow in the case of Turnkeys, especially because you're already up for an extra layer of costs. 

Now the terms at these auctions are usually $5,000 Deposit in Cash or Certified Funds due the day of auction; balance to 10% due within 5 business days, and Close in 30 days.

You mention the owner has paid $70k on the mortgage but that isn't a number that matters (since who knows what interest rate he's on or if he's made any extra payments), what matters is what the outstanding balance is on the mortgage and can you offer them a purchase price that is A) Fair to the owner, B) Helps them sell with some amount of equity and C) Gives you room that it financially makes sense.The numbers change based on if you want to flip it or rent it, making the question "does it make sense" different based on the direction you choose.In short, I have no idea how much I would offer...

Do management companies usually take care of grass/snow/minor issues in the ten percent or do they bill it out extra?

Also my estimation on rehab has about 20% extra for unknown.

No extra charge.