Tenants Want Out 4 Months Earlier - Termination Fee?

[Corey Schaecher]

I have three friends living together in a house who are splitting rent, but they're not getting along any more and all want out of the lease now.  Their lease is set to expire September 30, 2017 and they want to be out June 1, 2017.  

I was planning to charge 2 months rent as a termination fee.  Does that seem appropriate being that there's only four months left?  I have to turn the house over and find new tenants (Dogtown area in St. Louis).

I welcome any thoughts.

Corey