The website on Cushings goes over the testing on this page
Costs vary area to area so widely its hard to say how much something might run.
As cash flow is an issue here are some groups that might help you afford the vet bills including a health care credit card (carecredit) that can be used for vet costs so you can pay them off slowly:
American Animal Hospital Association
" Through the AAHA Helping Pets Fund, veterinary care is possible for sick or injured pets even if they have been abandoned or if their owner is experiencing financial hardship."
Angels 4 Animals
"Our services range from financial aid to complete treatment
to those pets and pet owners in need."
A credit card company for health care, including veterinary care.
"With a comprehensive range of plan options, for
treatment or procedure fees from $1 to over $25,000, we offer a plan
and a low monthly payment to fit comfortably into almost every
God's Creatures Ministry
"This fund helps pay for veterinarian bills for those who need help."
"Our efforts focus on serving the elderly, the disabled, and the
"We are dedicated to insure that no
companion animal has to be euthanized simply because their caretaker
is financially challenged."
The Pet Fund
"The Pet Fund is a registered 501(c)3 nonprofit association that
provides financial assistance to owners of domestic animals who need
urgent veterinary care."
United Animal Nations
"The m ission of LifeLine is to help homeless or recently rescued
animals suffering from life-threatening conditions that require
specific and immediate emergency veterinary care. We strive to serve
Good Samaritans and rescue groups who take in sick or injured
animals. In certain cases, LifeLine can also assist senior citizens
and low-income families pay for immediate emergency veterinary care."
They also keep a list of local and national help resources here