Can my elderly parents pay for my home remodel so they can move in with me?

Is there a federal law granting guest homes on existing property to care for elderly parents?

If you are a Power of Attorney for your elderly parent you can't accept a gift or money.
You can hire someone to do this what your asking.Must keep records to show the remolding.Can't go crazy spending wild for your benefit.

Is this something you are still working on. There are many alternative financing including the government.

yes, but be certain that you let other family members know what is going on. And you may want to have a formal agreement written up with your parents to cover any issues that may arise.
And that answer of course is contingent on laws in your state and county. Having an agreement written up would help with any issues.

I think it depends on what you are remodeling for? Are you remodeling specifically for their needs or are you remodelling for yourself even if they were not moving in. If it's for them, they should cover the cost, if not .. I don't think they should pay for the renovation, however, you could charge them something per month for living with you for sure! Good Luck!