My name I Dr. Amanda and I am sorry to hear that Littleman is having labored breathing. I am very concerned for Littleman's health as labored breathing in cats is never something to ignore.
The following is a list of possible causes of labored breathing in cats and you will see why I am so worried about him:
1) asthma (the easiest to treat, but will last a life time)
2) congestive heart failure (very life threatening)
3) cancer in the lungs
4) cancer around the lungs in the chest cavity
Tests that can be helpful diagnosing a breathing problem in cats start with x-rays of the chest. If there are no good answers there, then blood work may be helpful as well.
I know you said that you have financial concerns, but I am very worried that Littleman may not last until then. Do you have a local humane society near you? They often have a full service veterinary hospital open to the public that is usually less expensive than general practices. You also can consider Care Credit. This is a health care credit card that you can use for yourself and your pets. You may also explain your situation to your regular veterinarian and they may let you pay some now and some after payday. Lastly, the ASPCA has an entire page dedicated to folks who want to help others with their vet bills. Check that page out at https://www.aspca.org/about-us/faq/financial-help-my-vet-bills.
Good luck to you and Littleman,
I hope this answer helps you. Feel free to contact me if you have any further questions.
Kansas State University
College of Veterinary Medicine Class of 2001