Nobody can predict even 5 years out let alone 50.

I have a CO detector that plugs into an electrical outlet. 

A bad roof and HVAC don't rule out a property as a good investment as long as the numbers work.Inside the property, I look at outlets (Three prong outlets are good, two prong could mean the electrical system is dated), possible water stains, water heater, and general layout of the home.There's a plethora of other things to look at but I wouldn't say anything is a "deal breaker" so long as the problem can be addressed and the numbers still work.

And you'll have new cracks in unexpected places, old cracks that will not close, but instead enlarge.

Did you come out on fire, or hit some unexpected hurdles?

We figure out the ARV and back into our "strike price" but subtracting rehab costs, sales costs, a reserve for contingencies (unexpected items that pop up) and our profit margin...meaning we spend time thinking about our bids.

This was an unexpected $1,700 repair.

I couldn't agree more that people do have to go in with eyes wide open and it is demanding in ways that are unexpected.

Find something that you can enjoy and still make money.As @Frank Wong mentioned your expenses will continue to rise and while $4,500 a month seems like a lot there are always unexpected things that happen in life that will be more than $4,500.A few years ago I was burnt out as well with my corporate job and went through a career transition. 

With news outlets saying the market is crashing it will cause many projects, and rehabs to be postponed.