I own a crime scene cleanup company (
Raven Recovery Crime Scene Cleanup | Mayra Martinez 541-232-3036 * Michael Barrett 541-844-5004) and in my experience, insurance companies not only pay for the cleanup, but prefer it's done by a professional company. Hosing down a scene is not only illegal, but a huge risk to public health.
On a side note, there are enzymatic cleaners that we use to remove biohazards, and while most people immediately think of bleach as the perfect cleaning solution, hydrogen peroxide is actually the cleaner of choice. It foams in the presence of biomaterial.
By the time we get on scene, the blood and other material is usually dried up, coagulated, or otherwise harder to clean than if it were done immediately after the incident. Blood and body tissue travel an amazingly long way, so a reputable company checks everywhere for bits and pieces.
For you novel, and personal knowledge, I guess, police and other first responders are usually not allowed to refer a specific crime scene cleanup company and will usually advise people to check the phone book or internet. While I've never seen it, I imagine there are some companies that will listen to a police scanner and try to show up at the scene and leave a card or speak with a home owner, sort of ambulance chasing.
Another little detail to lend authenticity to your novel: It's more than the blood and body fluid that needs cleaning. Paramedics will leave behind a ton of tubing, equipment wrappers, even gloves. Police will leave behind fingerprint dust, gloves and crime scene tape. There's a good chance blood will be tracked to the door everyone's using to enter and exit the scene, and if there's a pet, that's a whole other issue. Imagine Fido scared, upset, tracking blood all over the house, and having to be dealt with.
Sometimes, because people don't know who to call, they try to clean the scene themselves, or their church will send in members to help out. Bad ideas all the way around. Crime scene companies are expensive for a reason, and worth the cost.