Amputees could make a living - after all, they had to - in the 1860s and 1870s. How good a living it was depended on their social status and education, though. It wasn't like the government or the private sector went out of their way to help veterans much. So, depends on what kind of person he is. IN the days before performance reviews and health liabilities, employers saw no problem hiring disabled people for jobs where thir disability would not immediately impede their work (one-legged store clerks, one-handed teachers, telegraphists missing a foot etc.). Immediately after the war, contacts or memories might even help getting hired (say you lost your leg at Fredericksburg, and your employer's brother fought there). But if you depended on manual labour to make a living, your chances were slim. There was always a sufficient supply of healthy, often cheaper immigrant workers competing. Of course a man in his fifties getting wounded in battle would almost have to have been an officer or NCO, which would give him a useful pension and skills to translate into a whitecollar or management job. Or a Southern militiaman, in which case he's probably screwed.
As to life expectancy, that depends on an aweful lot of factors, but generally the answer is 'you can't say'. The general expectation was that someone who survived the ampoutation and healing procxess was basically fine and would go on living as normal, and many did. but there are lots of potential complications (see your other thread) that can screw with that. Even without severe PTSD (something people did not understand at the time, of course), trauma can take years off your life. A lot would depend on the situation that person finds himself in after recovery. Someone who is integrated, productive and appreciated is likely to live a pretty much normal life, barring physical issues. Someone dependent on charity and/or an inadequate pension, probably not so much.