I think the sweet spot is in the $320-350K range.  

Sweet I just gained a few extra inches of ceiling height!

Sweet.

If you can buy a property for 25% down but depreciate 100% of the value over 4.4 years, that's a pretty sweet deal.)- Corporate structures can be used and are relatively inexpensive on the scale you're talking about.

We can make hundreds of thousands by appreciation so why sweet about 100-200$ cash flow per unit?

I'm very new to all of this so I only have 1 deal and it's my best one :) My wife and I bought our first home, a townhouse just outside of Nashville.Paid $137,500Remodeled and replaced HVAC for $15,000Reappraised for $165,000Got a HELOC for $12,500Purchased a new $300,000 house 10 miles from downtown with the Heloc as the down payment.Our mortgage/escrow/HOA on the original house is $1,000We rented the house to a family for $1,550.2 years later it's valued at $200,000.We just expanded our HELOC by $20,000 to help us purchase a mobile home park that has a $400-500k upsideOur current house value has grown $25-35k.Pretty sweet deal for a grand total of about $25k original investment to create all the above deals.

That's the sweet spot.  

This area has appreciated quite a bit, and finding a duplex for under $200K may be tough, but other central city neighborhoods like, Five Points, Beacon Hill, Dignowity Hill, Tobin Hill, Alta Vista, etc. may render some sweet deals.  

It was sweet! 

That's pretty sweet!