Yes, the knowledge component isn't enough.  

I'm definitely very interested in the appreciation component that's a great play for scaling quickly with the equity built up.

The cashflow component is what will make the difference in being able to hold them long term or needing to sell them after a few years.

IRRs like this are very suspect and are likely not imputing the labor component of the poster.  

It would have all the major components listed out (roof, bathroom, kitchen, HVAC, etc.) and for each component a few common tasks (roof sheathing, roof maintenance, replace roof, etc.) for each component. 

Adaptability, liquidity and constant management are key components to the success of any business.Theres alot of great suggestions in the responses, but in the end it's all up to how you want to run your business.Very best to you 

Go on the facts.White vinegar applied to animal urine, smoke etc will initially blow you away.