@Heidi M. what does your lease say about people living there that aren't on the lease?

You should have a separate operations entity - that will do all the public interfacing, property management, hiring of contractors, leasing, etc.

Me and my friends moved out on june 6 and submitted the keys that night in the dropbox of the leasing office.

My tenants called today informing me they are breaking their lease and moving out. 

Also they seem very happy that with 2 weeks to go until completion and they have 50% of the building pre-leased... maybe that is a good thing, but that really is only 3 units, I read that as they couldn't get another 3 tenants to rent in that area for that price point.    

There are tenants still living in the property.Is it better to simply evict them and start over or should we post notice that we will be needing them to sign a lease?

A tenant who wants to stay in a property indefinitely at the current rent could theoretically schedule an inspection and freeze their rent and lease.

For that matter there's still a lot of Eastern CO that is relatively inexpensive that could be used as a hunting lease or share cropped with a farmer.Just a few of the more "out there" ideas.

Do I have her parents cosign on the lease?

For now, creating a PM company to change the feel or just having properties under an LLC  does the exact same thing.DBA is good if you want to keep your personal names and address out of the leases and stuff.