It may seem like a joke about the excesses of rich people, but trust funds for pets are a real thing, and they're increasingly popular for people of all income brackets as a way to ensure their beloved animal companions are cared for.

But, if it's more common for pets to have trust funds, what actually happens to those pets when their owners pass away?

Some pets are entrusted to family members or friends, and these arrangements are made before the owner passes away.

But sometimes those pets end up in shelters — and shelters just want to find the perfect new owner for the animal.

Real-life examples of trust fund pets that found new owners

You won't earn money from a trust-fund pet, but you may not have to pay out of pocket for expenses either. You won't earn money from a trust-fund pet, but you may not have to pay out of pocket for expenses either. (Photo: Anna Hoychuk/Shutterstock)

Take the example of a Mill Valley, California, woman who is on a fixed income but had searched for some time for a pet cat. ABC 7 News reports:

Lynda Kline adopted her cat, Ayngel, about a year ago. "She loves to cuddle in my lap and the company is great for me," Kline said. Kline lives on a fixed income and never thought she would be able to afford a cat. But she wanted one so badly she would surf the internet and dream.

"One day, I couldn't resist going on Pet Finder. Lo and behold, I saw something I have never seen before - a cat with a trust fund," she said.

That's right. Ayngel is a trust fund kitty.

The story of Lynda finding Ayngel isn't as rare as you might think. Last summer, a rescue group in Oregon got a call to help find a home for five cats together. The five felines were left with a trust fund to cover food, litter and medical care for the rest of their lives.

And as of the ABC 7 News report, the same rescue that placed Ayngel with Lynda had two more trust fund cats — Oliver and Sammy — up for adoption.

While the trend of trust funds pets is growing, there are some pitfalls.

For starters, don't go looking to try and make money off animals with an inheritance.

Trusts are typically set up so that the adopter doesn't get money directly, but rather expenses are paid directly by the trust, or the new owner gets a stipend to cover costs. And sometimes trusts are very specific.

"For example, if your cat only likes a particular brand of food or your dog looks forward to daily romps in the park, this can be specified in a trust agreement," the ASPCA explains. "If you want your pet to visit the veterinarian four times a year, this can also be included."

So while you might have cost of care covered, you may also end up with very specific care instructions. And though you won't come into a wad of money by adopting a trust fund pet, you just might find a friend for life who doesn't carry a financial burden.

If you're looking for a pet while living on a limited income, start networking with local and national rescues. Begin conversations with shelter workers to let them know the kind of pet you're looking for, and that you're seeking one that has a trust to assist with the costs of care.

It may take some time, but if you're persistent with your search and stay on top of the networking process, you just might find your perfect (and paid for) rescue pet.

Jaymi Heimbuch ( @jaymiheimbuch ) focuses on wildlife conservation and animal news from her home base in San Francisco.