I need to be able to show all results of my view initially but then only show 1 result after the user selects their options form the exposed filters.
For the record, this seems like a really odd thing to want to do! How would you narrow it down to a single result if more than one matches the filter?
Anyway, you should be able to use this hook: https://api.drupal.org/api/views/views.api.php/function/hook_views_query_alter/7
If you check for the existence of filter values, you can then apply a "LIMIT 1" to the query.