Hi, I can help you with your question today.
After reading your post, I do think it would be wise to request a written estimate prior to any future care for your pets.
This is perfectly reasonable. As I see it, everyone has financial boundaries, and we aren't doing anyone any good if we step outside those boundaries!
Now, with regard to urine sample collection, we have a few options in front of us.
My preferred sampling method is through something called cystocentesis. This uses a tiny needle to obtain the urine sample. Obviously, this would need to be done at your vet.
If they didn't offer this, it may be something they aren't comfortable with, or perhaps they do not have ultrasound on site.
There may also be a cost incurred with this, so you may want to avoid it for that reason also.
In terms of home options, you can purchase a couple of different types of products to help with urine collection.
These are litter replacements, similar to what your friend had described to you.
One product is sand like, called Kit4Cat.
The others are plastic beads, like Nosorb or PawCheck.
You should be able to order these online if they aren't available locally or through your vet.
Please let me know if you have further questions. I am happy to continue until I provide the service that you seek.