In most states and locations there's no legal requirement to use a funeral home or funeral director to carry out the funeral and burial.
However you will likely want a funeral director to help use their equipment to lower the body into the ground but then again my Grandpa was lowered into the ground using the front bucket of a tractor and some straps.
But if you don't have a tractor you can also use ropes or other straps to lower the coffin into the ground but the equipment that a funeral home uses is much easier.
You can also keep the body at home if you desire until the burial of the body and all you will need is proof that the person died of natural causes or other death.
You can then also legally transport the body yourself to the grave site or even out of state yourself and you'll need to get a body transport permit which is mostly just showing that you're transporting the body legally and didn't murder them.