Who can I contact to hire someone to clear out dirty home after moving to assisted living?

You don't say where you are. You might Google hazmat cleanup since the urine and feces if human can constitute a biological hazard. Most larger cities have companies that specialize in certain types of cleanup if you are trying to sell the house. A regular cleaning company might take it on but don't count on it. You don't want health dept issues when prepping to sell.

There are estate sale companies...but the one business that comes to mind with a hoard is 1800gotjunk see if you have one in your area.

A good starting point would be to google "hoarding cleanup specialists" for your area. There are companies that will evaluate and do the work. This usually includes sanitizing and disposal of materials. One thing, though, is that it will not be cheap. Is there money to pay for this specialized work?

Another thing you could do is hire a crew and arrange for trash to be removed. They can clear the rooms and put the stuff in a dumpster to be carted away. If the area is not a biological safety hazard, this could be a way to go. It will still be expensive, but not so bad as the specialist companies.

BTW, if there are urine and feces, you may want to go the specialist route. You wouldn't want inexperienced workers to get sick.

Do you have POA? Is your friend competent to sign contracts?

Yes have POA but he is also competent enough to sign.

There is some money, obviously don't want to go crazy but I want to handle it properly. I've found a couple places I can call for estimates now after googling. Thanks for direction.

These would be companies that specialize in post disaster clean up. The cleanup you describe would be similar to after having a fire or flood. Mitigation companies.