I charge at least a 1.5x of the rent for a deposit so they are usually highly motivated to clean well enough to pay the last month's rent and get their big deposit back.This is usually good enough for the next tenant.

My concern is on fix and flips. is the market good enough to sale updated properties fast?

It’s just not good enough for me.

Any priority mail with tracking is good enough. 

I would advise people to use the Dave Ramsey method to get themselves in a good enough position to where they have no debt and then have enough money to put down at least 20% on a nice cashflowing property, and then rinse and repeat.

The return may not be as good as you finding a great deal on your own, but what turnkey company is offering is good enough for you, maybe it's worth it, especially if you don't have to do all the work.

That's no longer good enough.

It will not work well to try that at even the C+ or lower level ir if you have too many or if you have a good enough paying job and value your time more. 

Not necessarily a deal breaker if the price is good enough to justify that issue.

Or if it was mailed USPS with tracking, that should be good enough.