One of them walked out of his job 2 months ago and won't pay his share of the rent or contribute to cleaning the apartment in any manner.  

Generally, if a company conducts business in a professional manner, i.e, has gone through the time, expense and effort to have proper licensing, insurance, etc and has a record of longevity, they will be reliable.  

While the demand is real I can't believe this rate can be sustained.

Not only would you be helping to sustain the market, but you would also be able to increase the value of properties in certain neighborhoods by buying an eye sore, rehabbing it, and returning it to the condition of the neighborhood standard.

They will appraise the property for you as well as get the balance sheet to make sure the home can sustain that debt. 

Yes investments have risk and fluctuate but if they give a range for returns they stick in that range, we there they themselves make money or not. 3) They can communicate in a timely manner, often times they can’t answer back right away and that is ok with me, but within the next few days. 4) Experience is important, and if they are new make sure they either have a co-sponsor or are somehow giving the investors way extra to compensate for the lack of experience.

Quote from @Abby Thomas: When you buy an investment, the money it produces should sustain it forever with no need to put another dime into it.

We are always here to support with any issues that may come up, but more importantly to assist you in scaling your portfolio over time to build a sustainable business model! 

Thank you @John Manner 

Rather than sustain a large special assessment in the future, we decided to sell and use the money elsewhere.