Using an external hard drive as the only hard drive for iMac
My son's internal hard drive failed. He has an iMac from 2009. We have an external hard drive that we could use to connect to that computer and basically just use that computer as his monitor - but I need to know if that's even possible. We absolutely cannot afford a new internal hard drive for his iMac, so at this point it's just a brick. I do have my own iMac I can use to transfer operating systems and files onto the external hard drive. I'm fairly computer literate, but this is beyond my skillset. Can anyone help with recommendations or info on how to do what I'm trying to do? Thanks.
iMac Line (2012 and Later)