How can I find users by field value?
ElementCriteriaModel supports 'users' as well as 'entries'.

$criteria = craft()-&gt;elements-&gt;getCriteria(ElementType::User);
$criteria-&gt;relatedTo = array(
    'targetElement' =&gt; $currentUser,
    'field'         =&gt; $employer
);
$employees = craft()-&gt;elements-&gt;findElements($criteria);