lets say
you want some money so you take out a 500,000 dollar life insurance plan and then soon after you fake your own death. the money goes to spouse or whoever, and you come back a few years later/move away.

do insurance companies have to have a body?

could this work? if so, how can i improve it?

first u need a cadaver resembling your build.
if u have dental records u would need to pull your teeth and replace them with the cadaver. If your DNA is on record your fucked and just stop reading bc they can get the bone marrow.
This is done very often so insurance companies know what to look for. Lets so u get a body, put your teeth into it now what?

You're going to have to create a death. Just watch CSI and Without a Trace and those shows to come up with an idea.

Needs more planning but there is a start. Hope it helped. Good Luck!