Regarding location it should be close to the trendy areas within walking distance or short cab ride of restaurants/entertainment.....

To see if that trend is occuring in your area check around and see if forclosure rates are rising strongly and the vacancy rates of both houses and apartments are dropping steadily.

I believe this trend is happening in other urban areas, notably New York.

Your property manager should be fully dedicated as their property manager, not double duty with flips.Marketplace business model is becoming somewhat trendy. 

Ultimately its up to you so do your due diligence on the market (see homes and get online and look at homes for sale that have been remodeled) and the remodeling trends (know what is trendy/unique vs. standard practice in your area). 

There is this grey color by mohawk that I like, but I have hardwood floors in the kitchen and I am not a designer nor do I have any sense of what may be trendy or considered tacky these days lol.

Bottom line: if a tenant sees "trendy", they won't be thinking "cheap".

I am also a real estate agent and Salem is getting attention from my younger buyers and renters looking for a trendy place to live outside of downtown Boston.  

If the trend is improving I look at the other metrics you mentioned.  

I own a dozen properties in Uptown ( trendy/high demand) and have a 7 year vacancy rate of substantially less than 1%.