I regularly train in my basement. I don't use live ammunition.
I wish I never sold my Crosman 600.
I could practice in my basement with live fire if I had one of those.
Most of the ones you see on gunbroker are of the 'we figure the original owner stuck it back in the box when it quit working 40 years ago, so we're not going to put CO2 and pellets in it and tell you if it works before you buy it' variety.