VALIDITY OF CONTRACT

hi, po gusto ko lang po tanungin about sa contract of lease na pinirmahan ko I signed a contract kasi (so stupid of me) and pero wala sa harap ko yong lessee bale representative lang nya. so when i signed it wala yong lessee wala ring witness na nag sign. i signed it ang kasama ko lang din ay minor children ko.ipapa sign na lang daw nya. i did not give my sedula din. but i did not receive any payment para sa rent. after signing the contract saka lang sinabi na this week pa lang ibigay yong money. ang tanong ko po is that contract valid? if it is valid pwde po ba ito ipa void and how? at if it is valid paano po ako makapagdemand ng payment. please give me legal advice. thank you.