I am offering 15% interest on the initial investment plus 40% ROI after a six-month grace period.

This is a very valuable skillset to have in your arsenal as an investor that can dramatically increase your net worth in a short period of time if the strategy is applied correctly.  

I've seen many landlords that get lucky with good renters for a long period of time, then everything falls apart when they have to deal with real difficulty.I looked up your property on Google Maps, and the street view looks bad.

Complaints are always dicey when you live or have property in a jurisdiction they scan your license plate and have visibility into your property that may negatively impact you in the future.  

I'm <5 years from retiring, so in this time period, I'd like to build a portfolio of turnkey rental properties. 

Those are some amazing #’s in that short period of time.

We rotate locks through our rentals, with a period of non-use for each lock.  

Let's assume that the neighborhood is a C class and the median income of the city is greater than 3X of the market rent.Here are some of the considerations I've come up with so far:- Units are in need of renovation and capex is too high or not available- Unit quality is not the same as market - Seller is worried about losing tenants due to increase- Vacancy rates are high or filling units have been difficult- Rent increase would take multiple increases over multiple lease periods to get to market rate if seller is trying to retain the same tenant- Seller inherited property and just want to liquidate- Seller needs to liquidate quickly (financial burden, sickness, quick exit from land-lording)It seems like I might be missing a warning sign about a deal if they are selling with current rents that are under market; but again, this seems to be most of the properties I've underwritten.And in the same vein, what should I be worried about when purchasing a deal with under market rent with the intention of raising them after purchase. 

  ( I keep 30 tons on hand before each storm ) We are sending trucks and men out in terrible conditions for long periods of time , at all hours of the day .

Also, I believe I saw somewhere that the mortgage won't count against the original owners DTI after a period of time if they show someone else is paying the mortgage.