They are a popular topic online but used very rarely in practice. 

There are lots of quantitative metrics ("mainstream" as you say) to observe here (P/E for the S&P - see chart below, margin levels, ratio of total market cap to GDP, etc), & anyone with access to google can see the same numbers.

@Chris Heeren, I understand and agree with not wanting to be leveraged 100% of the ARV; I actually had a conversation with my wife after we got close to the closing date, realizing that we actually payed to much from an investment standpoint, not because of the numbers, but because we lost access to the capital that we put into the property.

Anyways we have found a build job opportunity for 3, 4 plexs (12 units) but it is a build job from a builder that isn't known and I really cant find much information about them online.

Hi @Jake K. and welcome to BP, it has everything you need from free online educational videos to connecting to other investors, you can't go wrong on this site!

With things going more and more online I wonder if lead gen websites will be more effective in the future.

Hello everyone,My Husband has been an Iron Worker for 12 yrs and was recently given access to his Missouri annuity since we've moved to California, where he is building up a new one.

., but don't want every eyeball out there having access.

Running it through an online ROI calc, it yields 25.5% per year for 7 years.

While I've never met either in person, they both seem great online.  :-D