With that being said, don't immediately make changes if you don't see results immediately... however if the ROI is consistently low, then you should be figuring out a way to improve the marketing.  

I bought my first property cash ($45K) and put ($15K) into it for improvements (new kitchen, appliances, paint, turning the attic into a 3rd bedroom among other things).

You want to be really careful to not over improve, but if you can get them looking a little nicer than the surrounding properties, you can attract better tenants.  

As the area continues to turn around I plan on gradually making larger improvements, most notably washers/dryers in each unit and roof decks the units.

. - More and more of the "bad" areas are getting rehabbed, so over time, they could see some improvements.

Not just due to overall market, but also do to location improvements (BART, up and coming complex, etc.)As you alluded to, be careful with a double ended agent deal, especially if it's your first.

Since you're now trying to improve and resell, it would be best to use seller financing for acquisition. 

If the other 6 all need $2,00 of new appliances and HVAC improvements then that will not be very fun.  

@Trevor Ewen  I'm sure it's just me but as a buy&hold investor, I'm focused on the performance numbers of the property and not concerned at all regarding tenants. 

To overcome this obstacle, you may want to look for a non performing building with a motivated seller.