By passing the meta key parameters. you can filter you posts.
$args = array(
'post_type' => 'post_type',(optional)
'meta_key' => 'age',
'meta_query' => array(
array(
'key' => 'loan_min',
'value' => $amount,
'compare' => '>=',
),
array(
'key' => 'loan_min',
'value' => $amount,
'compare' => '<=',
),
),
);
$query = new WP_Query( $args );
You can try with this code.
For more query you can visit this site: https://rudrastyh.com/wordpress/meta_query.html