I left out the important details about how much work the house needs: new windows, roof, no AC, not even a fume hood in the kitchen, sometimes mold issues in the basement, broken windows, landscaping. we basically self manage which is at times frustrating.

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.

They don't require any deposit or down payment at all, but they want all my details.. 

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.

I have done a lot of analysis on MLS listings including the more detailed Frank Gallinelli version of using NOI and cash flow to derive IRR and shortlisted 4 multifamily units from 100s that I looked through that I want to pursue and which offer a good COC and cash flow per unit.

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. 

The situations I deal with are far to many to detail here.

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?

Please PM me if you are able to do any of the above and I will give you more details.