According to
this the Vikings have $45,273,861 cap space for 2018. This is without the Cousins contract accounted for.
He have heard $28 million on average per season for 3 seasons fully guaranteed, but we don't know specifically how much that number is for 2018 yet.
If we subtract $28 from $45 that means the Vikings have $17 million in cap space remaining after Cousins contract is accounted for.
The numbers above list Shariff Floyd as almost $7 million against the cap. This will be cleared once they reach an injury settlement with Floyd. So that means $24 million left on the 2018 cap.
They already asked Murray to take a pay cut. They may end up releasing him, if they do this frees up another $6 million in cap space, which then would give the Vikings $30 million left to work with.
Another cut they may make is Brian Robison which could clear another $4 million giving the Vikings $34 million in cap space. Jarius Wright could be cut as well which would free up almost $5 million in cap space.
So if they cut the above players the Vikings would have $39 million still to work with.
I think this extra money is likely best used to re-sign players such as Stefon Diggs, Eric Kendricks, Dannelle Hunter as better options than players they could sign in free agency.
They may want to keep Trey Waynes as well. I have read that the Vikings are looking at nickle corners though, not satisfied with how Alexander played there and its not certain if Terrence Newman will be back or not. I am expecting Newman will be back another year, but the Vikings may not want to play him as much as they have recently. He is 40 years old.