Having a good PM to operate and market your STR is critical to profitability.

What Engineering taught me that was helpful in REI:How to think analytically; critical thinking; problem solvingThinking in terms of probabilities instead of absolutesUnderstanding how to model something, but also understanding the limitations of doing thatthe concept of margin of safetyrisk management and contingency planningdrafting and design of property systems, layouts, etc.technical project management ... projecting and controlling project scope, budget, and schedule ... this is more project management, but also has elements of systems engineeringroot cause analysis and other debugging methodsprocess, procedures, and control systems, which can include business systemstesting, verification, and validationAll in all, a great base of knowledge for REI, which is why so many successful investors come from engineering.

Housekeepers:  This one is critical because finding people to clean is easy but as you know this is SOOOOO much more than just cleaning.

Communication with the tenant is critical.

If condos are a viable option, I will need to research the time to rent and length of stay for each complex under consideration.Before recommending condos, it is critical to analyze rent growth.Inability to obtain investor financing could kill condos as investments.

My brother in law, who owns several rental homes, said the most critical part of a deal succeeding is the property manager. 

Therefore, a critical location selection metric is that rents and prices are rising faster than inflation.

It is critically important how well the HOA is managed.Many HOAs try to keep the monthly HOA fee low, but then run short when major repairs need to be made. 

I will go so far as to indicate he has been the most critical member of our team (in part because I have never used a rockstar RE agent).However, I tried a different mortgage broker once who after having all of our docs for quite some time informed us at the 11th hour that they could not get us the advertised loan. 

Know everything about the area: The specific property is always important, but they area may be just as critical as an investor.