That most likely depends on whether or not, they want to keep going thru the rigors of all the work and can sustain some type of shape. It was/is a sacrifice for many (If you watch Dorian Yates interview) he tells quite a bit of what he endured and stop doing. He looks much more normal now and just trains people. Pretty average outcome I would guess.
Depending on what/PEDS they used, they may be pretty well off. Some others, may not be so lucky. I can think of a number of them from the 70's that are dead and most likely what they may have inundated themselves with during their youth played a large role.
Of course the competitive days for older ones are most likely hard to keep up or even get back, but with the onset of TRT and the older man, I know a guy or 2 that still keep in good shape. Powerlifting might be a little different with age groups etc., but if you are talking from a standpoint of earning money, pick another career...!
Robbie Robinson was in great shape for like 65 yo or something but he did not use much when he competed. Not like what some of the guys nowadays use. Arnold does not look like he has kept it up as much as some, but that guy has other irons in the fire and new mountains to climb. (I think that is another secret) Knowing how to adjust the training and still Stay Hungry for other goals. Ferrigno is still in pretty good shape or at least was a few years ago.
Al Beckles was still competing against Arnold in the Olympia back in the 80's and he was 65 or some ungodly age.
There is also an article going around the webz of, Where are they now? And it shows some 80's and 90's BB'ers retired and very normal looking in street clothes.
It can take it's tool on some, but so does many sports. Just look at what football/players are/is going thru.