Using Vee-validate to disable button until form is filled out correctly

I want to disable my submit button until my form is filled out correctly, this is what I have so far:

<form>
   <input type="text" class="form-control" v-validate="'required|email'" name="email" placeholder="Email" v-model="userCreate.userPrincipalName" />
   <span v-show="errors.has('email')">{{ errors.first('email') }}</span>
   <button v-if="errors.any()" disabled="disabled" class="btn btn-primary" v-on:click="sendInvite();" data-dismiss="modal" type="submit">Send Invite</button>
   <button v-else="errors.any()" class="btn btn-primary" v-on:click="sendInvite();" data-dismiss="modal" type="submit">Send Invite</button>
</form>

The above only prints an error message and disables my submit button after I've started inputting a value. I need it to be disabled from the start, before I start interacting with the input, so that I cannot send an empty string.

Another question is if there is a better way than using v-ifto do this?

EDIT:

 userCreate: {
        customerId: null,
        userPrincipalName: '',
        name: 'unknown',
        isAdmin: false,
        isGlobalAdmin: false,
        parkIds: []
    }

One way to disable a button until all the values you need are filled, is to use a computed property that will return bool if all values are assigned or not

Example:

Create a computed property like this:

computed: {
  isComplete () {
    return this.username && this.password && this.email;
  }
}

And bind it to the html disabled attribute as:

<button :disabled='!isComplete'>Send Invite</button

This means, disable the button if !isComplete is true

Also, in your case you don't need two if/else-bound buttons. You can use just one to hide/show it based on if the form is completed or has any errors:

<button :disabled="errors.any() || !isCompleted" class="btn btn-primary" v-on:click="sendInvite();" data-dismiss="modal" type="submit">Send Invite</button>

This button will be disabled until all fields are filled and no errors are found