Terraform | AWS | vpc_id causing apply to fail
I'll go out on a limb here and assume that the issue is actually in your "aws_instance" block and is likely the result of how you are assigning the security groups in the "aws_instance".

Copied from the first linked article, in the resolution: 

change 

security_groups = ["cloud9Test"]

to

vpc_security_group_ids = ["${aws_security_group.cloud9Test.id}"]


Two related articles:

https://github.com/KainosSoftwareLtd/aws-api-gateway-demo/issues/3

https://stackoverflow.com/questions/31569910/terraform-throws-groupname-cannot-be-used-with-the-parameter-subnet-or-vpc-se/34586893#34586893

If this is not on track, please post the "aws_instance" declaration. 

For your own sanity I'd also recommend giving the resources names that are more specific to their role, and not identical, for example "cloud9Test_vpc".