Retired men from the army

[Frank]

Isn´t it true that by the time a veteran gets retired he was rich enough to pay people to work the land for him?

As described above, he could simply take the land, lease it to coloni and live from the rents in a small villa. He could also lease less land and farm on the rest with a few slaves.
In imperial times he would get about 12.000 HS in cash (thats worth about 10-15 ha land). Assuming the usual rates of 5-12% on investments these times, he would get 600-1400 HS per year. Thats enough to live in the province, without the need to work actually. But with a risk of course.

Nevertheless I would'nt call a retired miles gregalis rich. It is not bad. Better than a day laborer in the cities or a small tenant. But not really rich.
A duplicarius was perhaps somewhat rich, because he got 24.000 HS and could also save more money during his 20 years of service. And of course the centurions with 5 to 15 times the pay of a miles. Not talking about primi ordines or primpilares.