I think most hosts give 5 stars unless there is a serious issue so even a 4 star is a red flag for me that I would check into. 

Also, real builders/experienced developers will often have a true technician, i.e. a civil engineer, architect, real estate attorney et al at least glance at the property info to make sure there are no major red flags.

It would be a big red flag to me if they are doing a lot of volume in this market. https://www.biggerpockets.com/member-blogs/10145/83067-limited-partner-s-guide-to-investing-in-the-right-deal

Our primary objective as coaches is to help clients ask the right questions, develop the right criteria, and identify potential red flags. 

Red flags all the way around. 

It is very unlikely that you'll have problems/be investigated for just one instance, but repeatedly doing this will absolutely raise red flags these days.

Because of them my proxibid account flagged.

Making a gross characterization. 

Shortly after, my strategist flagged that RTR was severing its ties with their PM partners in Harvest and would be seeking a new go-to team.

Are there any potential red flags I should be aware of?