Nowadays, cash-flow in SA seems to mean that it covers expenses, without much cushion for the possibility of market fluctuations after an extended period of appreciation, or unforeseen expenses.

What I would do would be a contract that requires you to provide a budget (which, in addition to actual improvement materials and work, would include your labor hours for management/oversight fee, or something to that effect, and of course a contingency for the unforeseen, plus cost to rent furniture for staging, etc.) and scope of work to be approved in advance by the Seller. 

It helps keep cash in the bank in case there are any unforeseen catastrophes that crop up but for the most part, everything is done in cash.

You can make it work with 80-85% ARV but it obviously gets riskier if things go wrong or there is an unforeseen repair.

It should be easy to come up with a number that will promote the GC to work quickly.Of course with change orders and unforeseen circumstances, problems can arise but this is what most mega-construction companies contracts look like.

No major issues, unforeseen surprises, etc.

unforeseen issues or contractor didn't have pricing right for materials/labor?

On the other hand, a savings account is also there for any unforeseen circumstances.

This can be a unforeseen cost over run.

Anyone that says otherwise is selling something.Also @Chris Schoonhoven I'll assume that the $80k you have available to invest means you have already set aside a meaningful cash reserve for unforeseen needs.