I live in NYC and started investing in Buffalo a few years back, mainly for the reasons that you mentioned. 

Rents increased about 5% per year, and when you take 5% on $3,800, that's almost a $200 per month increase for the year!

Sometimes, the more old-school approach like posting on local community boards can help you find reliable tenants.

It's a fairly unregulated space (charging grandma $750 to puts around for 3 hours, after moving the old box from the horizontal sensor, which was the only problem with the garage door to begin with), so some combination of carefully reading reviews (you have to actually read them to make sure it's not 200 fake reviews), and maybe not giving them the full contract all at once, is in order. 

My wife brokered a 6 mil house in Oregon even.. the seller was a Chinese bizzman who bought it for his 19 year old kid.. why he would need 10k plus sq ft I dont know..

Or would you just use the cash flow from your old unit to make up difference?

If the trade value of an old shopping mall is less than the build cost of a new storage space or warehouse, then it doesn't make sense to build a new storage space or warehouse, just buy an old shopping center.

And the tenants still lived there, they had just been putting old mattresses, broken furniture, and crud there for years.

15 year fixed mortgages are very underrated a 200bps spread is enticing as well as lower transaction costs.  

End of the year.