If the current rents are $1200 per floor and market rent is $1500 per floor, there will be some pain and suffering raising the rents, but LONG TERM the house has more value. 

My question is what is the best way the raise the remaining money?

It was a value-add opportunity, with a plan to do some interior rehabs, raise rents, lower expenses, and improve management, but now we are not so sure about those opportunities...at least in the short term. 

And tenants become concerned that rents will be raised.

@Alex JamaelBe careful raising private $ especially if you are raising it from multiple investors as there are a lot of rules on how to properly raise $.

@Antonio Foster check out this link for ways to raise capital for real estate investing.

Get commitments for way more than you need.There are great books out there on the topic, including Joe Fairless's Apartment Syndication book, Hunter Thompson's Raising Capital book, and others. 

@Jonathan Jones you are going to have to raise your real estate IQ immensely before moving forward with your first deal.

I raised rent $300 a month for the next two years and have sold it.

I raised rent $300 a month for the next two years and have sold it.