Help with a possibley sick cat?

My friend has 2 cats. One of them has not been seen for 3 days and she found it in the house and went to pick it up and had a vomit like substance one the bottom half of its body. it is a mixture of white red and brown. it is having difficulty moving its back legs abd she does not know what is wrong with it. we cannot get to a vet we have about 7 inches of snow outside please this is an emergency! we need help! what should we do? by the way the cat is about 1 year old