James 'Jimmy' Prout, of Percy Main, has not been seen since the start of February and police believe the 43-year-old has been killed.
A body, which officers say is likely to be that of Mr Prout, was found "in an area of open land" close to his home at 15:30 BST.
Two men, aged 26 and 42, and three women, aged 55, 49 and 25, are in police custody.
Mr Prout's ex-partner, Anne Corbett, 25, was also reported missing but has now been located.
Supt Peter Bent, of Northumbria Police, said: "We only became aware that James was missing when we received a call on Good Friday which identified concerns for his welfare.
"An investigation was immediately launched and our enquiries established that he had not been seen by friends or family for a number of weeks.
"As a result of searches police have found a body a short distance from his home address. Formal identification is yet to take place but we are fairly certain that it is James Prout."
Five people have been arrested on suspicion of murdering a Tyneside man.