In most cases with old painted walls (such as in older homes or apartment buildings) people tend to paint over with newer latex or oil paint. This is just a temporary solution, however.
If walls, and woodwork such as baseboards and trimwork appear to be in sound condition, you might choose to paint over the old lead paint. Do not sand, scrape, or do anything to release dust into the air, as you can breathe in the dust particles. It is probably safer, overall, to simply leave intact layers of paint undisturbed.
You can also choose to do what is referred to as encapsulation. This is where you cover walls and ceilings with gypsum wallboard (drywall), plaster, or paneling. Just be aware that you are, only covering up the lead paint problem and not actually removing it.
It is also much easier to replace the old lead-painted items such as doors, windows and trimwork yourself, than to try and strip off the paint. It’s more expensive to install new items such as windows and doors, but, you’ll remove the lead problem,making it safer, and add value to your home in the process.