And BOOM its popular again.

Syndications generally have been around for a very long time, and got more popular this cycle due to the JOBS Act.

I'm not sure where the popular notion comes from that there is a lack of demand in the suburbs.

I’ll spend more time doing research and reading those books you mentioned and will happily shoot you questions that arise during the meantime.I agree with your conclusion on OPM and once I have skin in the game I’ll peruse that option.

Sorry if it's not popular but we've been doing this for years and after building our personal home (with cash), we now are able to take all the profit from our rentals and current income and pour it into the business.

Most popular for a renovation loan would be an FHA 203K or a HomeStyle Renovation loan.

It's impossible for there not to be a rise in homelessness.

Virtual and site-unseen showings are becoming more popular due to the pandemic/social distancing and we have seen an increase in Renters Remorse. 

Has anyone ever put filler concrete in there to avoid future inspector issues that may arise when a flip the house?

This is one of the reasons people don't like it, because you are moving two complete strangers (from the tenant perspective) together and there is always a risk for confrontation and issues arising between them.