It is difficult to know for sure as landlords weren't able to file the typical eviction paperwork with the courts over the past 16-18 months that would normally be our source of public records.We are now considering asking for proof of the last 2 - 3 months' rent payment (their rent receipts) when these red flags come up.

Instant red flag for the IRS.

A low LTV is a natural defense mechanism because there's not enough meat on the bones for an attorney to go after.

How do you treat a potential tenant who none of his recent two years landlords are giving any info about him (I have called two latest landlords , they say either can't release due to confidentiality or we don't have the records )He has good credit score and no red flag in background check 

The only red flag I see is your statement "I would also like to make a hobby out of flipping houses."

Columbus is definitely red hot!

Thanks @Roy Cleeves that's exactly what they offered me at TD today.

It's just a bunch of red flags for me and I would not do it.

Are there any red flags/additional information I should look for when assessing a tenant's bank statement?

Gut feeling is a tricky one because sometimes (at least for me) I have overlooked the shady contractor/broker/seller and instead look at the potential of the project, only to realize when something comes to bite you in the butt and you realize all of the red flags in hindsight.