My little old Chihuahua Tyko is sick.

Hello my name is Lisa. I have a chihuahua that is ill. He is an older dog. His problem seems to be Rhino sinus based. He's sneezing constantly. There are some reverse sneezing involved. His nose is running and stuffed. He's mostly breathing out of his mouth. What comes over his nose appears to be whitish. I'm very worried and at this point in time I cannot afford to take him to a vet.