PLEASE HELP! Late 2009 iMac 27’ will not boot past start up screen

Late 2009 iMac 27’ 1TB HD 16 GB RAM

My iMac was fine until last week.

I tried turning it on, it slowly loads about 3/4 of the way and then shuts off, restarts, and repeats the same issue over and over.

Main things to mention:

I’ve tried every boot method possible, nothing works

ive tried Reset PRAM and smc.

Holding Command+R while starting freezes the boot screen 3/4 of the way and the computer doesn’t shut off or do anything it just sits there at the white loading screen, I let it sit for over an hour and nothing happened.

Ive made a bootable usb of the operating system this way I can try booting it through that by holding OPTION during start up, that also doesn’t work. Still loads 3/4 and shuts off and restarts.

Ive also tried to use target disk mode because I did not back up the computer and I need very important files out of it, target disk mode screen pops up when holding T, but on the other Mac that is connected, it doesn’t show the targeted iMac on finder not disk Utility.

Last thing to note. During start up, about a little less then half way through loading you can hear the hard drive stop spinning.

The fans only go on when you first start the computer

while the computer is loading 1/4 and even 2/4 way through you can here it reading.

Im about to give up all hope, I’m emotionally crushed by this because my files are stuck in this potatoe.

Oh, I don’t know if this will help but, when it was working.. I would rarely, almost never shut the computer off.. even if I’m not using it or during the night I would just put it on sleep mode.

somebody PLEASE, please please.. give me some hope or some insight on what it could be, how much it’ll cost to fix and if there is any hope of saving my files… I’m also very poor so buying a new Mac will not be an option