You won't know until you open up walls.

We have tried a dozen and ended up with our own custom built Podio platforms. 

Get as much understanding and disclosure as possible on the closing fees and escrows that will show up on the settlement statement - including stuff like prepaid interest ("stub interest"), tand and insurance escrow holdbacks, etc - biggest pitfalls we've seen are people not 1000% clear and aware of these things then getting very negatively surprised at the day of signing 

In that sense STR investors can make markets more efficient by picking up housing units that most typical buyers look over. 

After 7 times, I would for hell give up.

Start with a W2 and build up some reserves. 

I am an investor based in Fairfield County, CT and just rejoined BP after many years away.From 2005-2011, I got up to ~150 units in SF & MF both rehab & new construction, Class B & C, but (regrettably) sold all to focus on institutional real estate and private equity.Since selling off, I got an MS degree in real estate and participated in most asset classes institutionally ($10-250mm+) with a focus on SF & MF.

Is it worth getting a permit and setting up a vending machine in a multifamily, with 10 or more units? 

You will start to get the hang of it and put processes into place to stop or change the situation up, or just not buy the property because you know what they may run into. 

Flooring is an exception to this since LVP is higher priced, it does last a very long time for something that will get beat up over the years.