You can find a person who has the following qualities:-
Trustworthy: no relation can be strong if partner do not have trust on each other.
Maturity: your partner should be mature enough to stand with you in difficulties.
Openness: partners should be open to each other.
Honesty: without honesty no relation could be last longer.
Respect: partner should have respect for each other.
Love and affection: Love and affection is the most important quality of partners.