When pulling the credit report one of the individuals has a high debt to equity ratio (50 %) My fear is what if this High DTI and credit usuage could result in one of the parties defaulting on future rent.

AirDNA has tools where you can explore the metrics on individual cities down to single zip codes.

There'll be like-minded individuals who's brains you can pick as well:https://www.biggerpockets.com/forums/521/topics/1230348-pint...

And individual deals.  

I guess my question is, should I narrow my focus to one REI strategy or keep it broad and analyze each opportunity individually?

If a cash out refinance, many lenders will allow the cash out to satisfy the reserves requirement.DSCR lenders generally let you vest either individually or as an LLC.

If you do this once a year for 10 years, you will be very rich when you are old. 

I'd research how much the rich people from NYC are paying and see what kind of houses they're staying in.

Real estate is Get Rich Slow.

Personalizing your message to the individual recipient is the best way to avoid this.