As far s your questions goes,  I have had properties that were negative, and I sold them before they ate me up, but the vast majority were all newt positive CF. 

The vast majority of properties at their available prices will not meet this requirement.  

in a vast interview process with many steps before allowing someone to move in. a new roomie is an everyone-decision, not a landlord-only decision; if you're expecting people to co-exist in a space together (for longer than just a few months), you have to make sure they all have some things in common, or at minimum have the right expectations in terms of cleanliness and routine habits.someone working the night shift and someone else having a 5am rise-time, or someone who works from home in a call-center job is not going to jive well for example. and someone who doesnt handle conflict well is not going to jive with someone who is brutally honest and up front about issues. happy to go into more deets on how we do things if it will help. this can certainly be lucrative in terms of cash flow, but there are huge mud puddles i have stepped in over the years which i have had to learn to navigate.

I am guessing that the vast majority of homes 10+ years old had some sort of water damage at some point, most had probably several.My own home is only a few years old and we had the washer spring a leak and a few years later the RO system in the kitchen started leaking into the cabinet.Seller disclosures are pretty useless in my opinion.

If you are not building in sufficient capex, then these costs could be higher, if not much higher.

Incurring debt before you have sufficient earnings to support that debt.

Hard money costs do eat into the profit but a good hard money lender will want to make sure you are making a sufficient profit on the deal after holding costs, etc. 

So all my deals I put together or the vast majority had notes on them.

I was also impressed by their vast network and access to off market properties.

You have many options here.1) Terminate the lease: It clearly states that they must have renter's insurance and the lapse can result in a default2)Have them cover the damages with sufficient evidence that they caused it3) Claim it on your insurance for the property, likely they won't give a good payout unless a fire, flood, or some sort of wind damage.