We need to make some assumptions here. To me, it seems certain that the ex-soldier is suffering from PTSD. And that it's probably untreated, making him dangerous to himself and others. As well, we can discount the rent boy's motivations about paying for a mortgage.
The actual sex is rough and nasty. The soldier wants a connection but isn't doing himself any favours here. After, he shows a more vulnerable side, as far as a thick carapace of hurt and being closeted will let him. Is the hustler interested? I'll leave that to future viewers to find out.
There's a coda to the rather shocking parting of the soldier and the gigolo. As a way of releasing our shock and tension of the previous minute, it's effective and necessary.
A film worth watching.